Stabilised nickelophilic thiosemicarbazone complexes showing semiconductor and nonlinear optical properties

Abstract

The invention relates to nickelophilic thiosemicarbazone complexes and the synthesis method thereof. Said synthesis method is carried out in a single step, and by means of said method, metallophilic complexes with high solubility are obtained. In the invention, the syntheses of nickelophilic thiosemicarbazone complexes stabilised by the second sphere coordination interaction with the nitro substituted aniline compound are described, and the structures that are the subject of the invention exhibit NLO (non-linear optical properties), semiconductor and chromic properties.

Description

[0001] STABILISED NICKELOPHILIC THIOSEMICARBAZONE COMPLEXES SHOWING SEMICONDUCTOR AND NONLINEAR OPTICAL PROPERTIES

[0002] Technical Field of the Invention

[0003] The invention relates to thiosemicarbazone complexes that are nickelophilic and have semiconductor and nonlinear optical properties and the synthesis method of these complexes. In addition to the fact that said synthesis method is carried out in a single step, metallophilic complexes with high solubility are obtained by means of said method.

[0004] State of the Art

[0005] With the rapid development of the information age, the internet, multimedia and other forms of information technology have become an indispensable part of people's lives. The rapid development of data, cloud computing, 5thgeneration mobile communication, the internet of things and artificial intelligence will be the next breaking points of economic growth. All this development increases the need for multimedia connection and service technology to process, transmit and store information faster and better. Chips, which are the main elements in the automotive and electronics industry, are produced using semiconductor materials (such as silicon, germanium, and gallium arsenide). Since germanium and gallium arsenide are not found in large quantities in the earth, they are difficult to obtain and therefore their costs are quite high. In addition, due to the increasing interest in semiconductor chip technology, a global supply-demand imbalance has emerged and due to the chip crises experienced in recent years, restrictions have been imposed on the export of many semiconductor materials, including silicon. This situation also causes high costs. In recent years, due to the rapid development of technology, especially in chip supply, problems such as slowing down production and increasing costs are seen due to the inability to meet the increasing demands. Especially in the automotive sector, some large factories have to take measures such as stopping production. This makes the discovery and production of new semiconductor materials very important. While some semiconductor materials can be easily obtained from nature (such as silicon), semiconductor properties can also be given to materials through physical interactions within or between molecules. Intramolecular or intermolecular hydrogen bonds, IT - IT stacking of arenes, Van der Waals forces, electrostatic interactions and physical interactions such as metal-metal contacts are an important topic in coordination chemistry since they lead to the formation of supramolecular, polymeric structures. Metal-metal contacts among these physical interactions are known as metallophilic and occur rarely.

[0006] Metallophilic interactions are very strong van der Waals forces, energies of which are approximately close to hydrogen bonding. These non-covalent interactions provide materials with very important properties such as luminescence, non-linear optical properties, conductivity, catalysis, magnetism and polychromism, solvatochromism, and thermochromism.

[0007] The study of Caplanus et al. in the state of the art relates to the electronic transport properties of some thiosemicarbazide derivatives that form complexes with nickel cations. Obtained organic compounds are thiosemicarbazide derivative compounds. The thiosemicarbazide derivatives that form complexes with said nickel cations show semiconductor properties, but do not show properties such as nonlinear optical properties, solvatochromism, and thermochromism.

[0008] In the study described in the patent application numbered EP3187504A1 in the state of the art, thiosemicarbazone-based supramolecular nickel complexes for CVD applications are described. In said study, it is mentioned that the CVD method is used in the semiconductor industry. This study relates to the use of the compound as a volatile solid metallo-organic precursor in CVD applications, especially to prepare thin metallic films of nickel, via the isopropyl alcohol it contains in its structure. The compounds obtained as a result of the study do not show metallophilic interactions and these compounds do not have semiconductivity and nonlinear optical properties.

[0009] Due to the difficulties and inadequacy of the solutions in the state of the art, it has been necessary to make a development in the relevant technical field. The present invention relates to a synthesis method in which the disadvantages in the known state of the art are eliminated, the synthesis step is reduced to a single step, the production of materials showing semiconductivity, nonlinear optical properties, solvatochromism, and thermochromism properties is made and the cost is reduced with the selection of chemicals used. Brief Description and Aims of the Invention

[0010] The invention describes nickelophilic thiosemicarbazone complexes and the synthesis method of thereof. Said synthesis method is carried out in a short time, and by means of said method, metallophilic complexes with high solubility at room temperature in water, ethanol, hexane, DMF (dimethylformamide), DMSO (dimethyl sulfoxide), chloroform, dichloromethane, THF (tetrahydrofuran) are obtained. These metallophilic complexes can be used as semiconductor materials.

[0011] The general structure of said complexes is shown by Formula X.

[0012] Formula X

[0013] In Formula X, R is R= - H or - NO2.

[0014] An aim of the invention is to provide semiconductor material. In the invention, nickelophilic metal complexes are synthesised. In the invention, delocalised electron density is created using thiosemicarbazone compound and thus semiconductor metallophilic complexes are obtained.

[0015] Another aim of the invention is to provide a semiconductor material with optical / electronic properties. The nickelophilic metal complexes synthesised in the invention exhibit semiconductor properties, but since they are obtained using nitro substituted aniline compound having both donor and acceptor groups, they also exhibit optical / electronic properties. The electronic absorption and emission spectra of nitroanilines are based on the proximity of the lowest energy excited state and the triplet states with n-ir* and TT-TT* characters. This facilitates electron transitions and due to these properties, nitroaniline group compounds exhibit NLO properties. The nitro substituted aniline compound added to the structure contributes to the nonlinear optical properties of the structure.

[0016] Another aim of the invention is to synthesise semiconductor materials in a short time at a low cost. In the invention, nickelophilic metal complexes that exhibit semiconductor properties can be synthesised much more easily and quickly with a simple process compared to the synthesis of commonly used semiconductor materials (germanium, etc.) in the state of the art. In said method, nickel (II) salt, which is more easily found in nature and more economical compared to other metals where metal-metal interactions are observed, is selected and hybrid nickel metal complexes that combine all the properties in a single material are synthesised. While the synthesis of such hybrid compounds requires multi-stage and expensive methods, said method is a cheap, fast and simple one-pot synthesis method. Therefore, in the invention, semiconductor materials are produced with a much simpler, faster and more economical method compared to existing methods.

[0017] Description of Drawings

[0018] Figure 1 Molecular structure of Complex I.

[0019] Figure 2 Molecular structure of Complex II.

[0020] Figure 3 Synthesis scheme of complexes and visualisation of intermolecular interactions, (A: Starting material, B: thiosemicarbazone complex, C: substituted nitroaniline compounds) (Visualisation of the structure including intermolecular hydrogen bonding, Ni — Ni interaction and TT-TT stacking with the formation of ONNO coordination mode)

[0021] Figure 4 Visualisation of Ni... Ni interaction in complex structures.

[0022] Figure 5 Molecular structure of the nickelophilic interaction observed in Complex I.

[0023] Figure 6 Molecular structure of the nickelophilic interaction observed in Complex II.

[0024] Figure 7 Comparison of UV spectra of Complex I and Complex II. Figure 8 Absorption spectrum of Complex I in different solvents (DMF, DMSO, MeOH, THF, i-PrOH, DCM, CHCI3).

[0025] Figure 9 Crystal structure of Complex I showing intermolecular interactions.

[0026] Figure 10 Crystal structure of Complex II showing intermolecular interactions.

[0027] Figure 11 UV absorbance graph of Complex I in DMF at hot and cold temperatures.

[0028] Figure 12 UV absorbance graph of Complex I in DMSO at hot and cold temperatures.

[0029] Detailed Description of the Invention

[0030] The invention relates to stabilised nickelophilic metal complexes synthesised in the presence of a nitro-substituted aniline compound and the synthesis method there of (Figure 3). The synthesised structures can be easily separated in the crystal structure and their solubility is high. Since said metal complexes can exhibit optical properties alone and have semiconductivity properties, the invention can be used in the production of optoelectronic materials.

[0031] The general structure of said complexes is shown by Formula X.

[0032] Formula X

[0033] Complex I, which is obtained when R is R=H in Formula X, is shown by Formula 1. Formula 1 is called N1 , N4-bis(salicylidene)-S-methyl-isothiosemicarbazidato- Nickel(l l).2-nitroaniline.

[0034]

[0035] Formula 1

[0036] Complex II, which is obtained when R is R=NC>2 in Formula X, is shown by Formula 2. Formula 2 is called N1 , N4-bis(salicylidene)-S-methyl-isothiosemicarbazidato- Nickel(ll).2,4-dinitroaniline.

[0037] Formula 2

[0038] The nickelophilic metal compounds synthesised in the invention are Formula 1 and 2, C22HigN5NiO4S (Complex I) and C22Hi8N6NiOeS (Complex II).

[0039] The colour of Complex I is brown and the colour of Complex II is brownish-red, the synthesis of Complex I using 2-nitroaniline (C6H6N2O2) as a secondary ligand shows 48% efficiency, and the synthesis of Complex II using 2-4-dinitroaniline (CeHsNsC ) as a secondary ligand shows 67% efficiency. The melting point of Complex I is 188- 189°C. The molecular mass of C22HigN5NiO4S is calculated as 508.17 g / mol. Elemental analysis calculation for Complex I C22HigN5NiO4S: By mass (%): C, %52.00; H, 3.77; N.13,78; S,6.31.

[0040] IR (cm1) spectrum analysis results for Complex I: 3479, 3302 (Aliphatic asymmetric and symmetric N-H stretching bands); 3157,2948,2869 (C=CH stretching bands), 1621 ( 6(N-H) ); 1604, 1599, 1578 (C=N); 1 140, 1 121 (C-O); 1543, 1345 (Aliphatic asymmetric and symmetric N-0 stretching bands);

[0041] UV-Vis analysis results for Complex I: (5.10-5 M, CHCI3): ((A (E)) 228 (11480), 240,5 (22140); 281 (8220), 300 (8540); 322,5 (6200); 395 (7700), 474 (2540), 549,5 (1460).

[0042] 1H-NMR analysis results for Complex I: (DMSO-d6, 25°C, ppm): 8.52 (s, 1 H, CH=N4); 8.33 (s, 2H, NH2); 8.30 (s, 1 H, CH=N1); 7.93 (dd, 1 H, Jxy= 1.34, Jxz= 8.72, x); 7. 74 (dd, 1 H, J= 1 .68, J= 8.05, d); 7.55 (dd, 1 H, J= 1 .68, J= 8.05, s); 7.45 (td, 1 H, J= 1 .68, J= 6.71 , J= 7.04, b); 7.37 (ddd, 1 H, J= 1 .34, J= 1 . 68, J= 6.71 , z); 7.33 (td, 1 H, J= 1 .68, J= 6.71 , J= 7.05, q); 7.00 (dd, 1 H, J= 1 .34, J= 8.72, w); 6.98 (d, 1 H, J= 8.73, p); 6.91 (d, 1 H, J= 8. 73, a); 6.71 (t, 1 H, J= 7.04, J= 7.72, c); 6.63 (t, 1 H, J= 7.04, J= 7.38, r); 6.59 (ddd, 1 H, J= 1 .01 , J= 1 .68, J= 6.71 , y); 2.71 (s, 3H, S-CH3).

[0043] Complex II is brownish-red in colour and has a 67% efficiency. Its melting point is 179- 180°C.

[0044] Elemental analysis calculation for Complex II CggHisNeNiOeS: By mass (%): C,47.12;

[0045] H, 3.84; N, 15.08; S,5.29.

[0046] IR (cm-1) spectrum analysis results for Complex II: 1625, 1606, 1584 v(C=N); 1160, 1123 v(C-O); 3449, 3332 v(-NH); 1540, 1388 v(-NO2).

[0047] UV-Vis spectrum analysis results for Complex II: (5.1 O’5M, CHCh): ((A (E)) 227 (1 1000), 242.5 (18240), 302.5 (9180), 326 (8720), 393 (7600), 475.5 (2700), 549 (1560).

[0048] 1H-NMR spectrum analysis results for Complex II: (DMSO-d6, 25°C, ppm): 8.80 - 8.46 (geni§, s, 2H, NH2); 8.77 (d, 1 H, J= 2.93, x); 8.50 (s, 1 H, CH=N4); 8. 29 (s, 1 H, CH=N1 ); 8.14 (dd, J= 2.93, J= 9.76, 1 H, y); 7.74 (dd, J= 1.46, J= 8.29, 1 H, d); 7.53 (dd, J= 1 .95, J= 8.59, 1 H, s); 7. 44 (ddd, J= 1 .47, J= 6.35, J= 8.3, 1 H, b); 7.29 (ddd, J=

[0049] I .96, J= 6.84, J= 8.79, 1 H, q); 7.09 (d, 9.76, 1 H, z); 6.97 (d, J= 8. 29, 1 H, p); 6.89 (d, J=8.29, 1 H, a); 6.70 (ddd, J=1 .46, J=7.32, J= 8.3, 1 H, c); 6.64 (t, J= 6.83, 1 H, r); 2.70 (s, 3H, S-CH3). Synthesis method of stabilised nickelophilic metal complexes that is the subject of the invention comprises the process steps of: i. mixing 2-Hydroxy-benzaldehyde-S-methyl-isothiosemicarbazone, 2-hydroxy benzaldehyde (C7H6O2) and nickel(ll) chloride hexahydrate (NiCl2.6H20) in methanol(C2H60), ii. adding 2-nitroaniline(CeH6N20 ) or 2-4-dinitroaniline(CeH5N30) as secondary ligand to the bright red solution obtained as a result of mixing and turning the colour of the solution to brownish red, iii. refluxing the reaction mixture and filtering, and iv. crystallising the filtered brownish red powder product and drying it under vacuum.

[0050] In another embodiment of the invention, the synthesis method of stabilised nickelophilic metal complexes that is the subject of the invention comprises the process steps of: i. mixing 1 -10 mmol of 2-Hydroxy-benzaldehyde-S-methyl- isothiosemicarbazone, 1 -3 mmol of 2-hydroxy benzaldehyde (C7H6O2) and 1 - 10 mmol of nickel(ll) chloride hexahydrate (NiCl2.6H20) in methanol (C2H6O) for 1 -10 hours, ii. adding 2-nitroaniline(CeH6N202) or 2-4-dinitroaniline(CeH5N30) as secondary ligand to the bright red solution obtained as a result of mixing and turning the colour of the solution to brownish red, iii. refluxing the reaction mixture and filtering, and iv. crystallising the filtered brownish red powder product and drying it under vacuum.

[0051] In another embodiment of the invention, the synthesis method of stabilised nickelophilic metal complexes that is the subject of the invention comprises the process steps of: i. mixing 0.21 g, 1 mmol 2-Hydroxy-benzaldehyde-S-methyl- isothiosemicarbazone, 0.12 g, 1 mmol 2-hydroxy benzaldehyde and 0.23 g, 1 mmol Nickel(ll) chloride hexahydrate (NiCl2.6H20) in methanol for 1 h, ii. adding 0.14 g, 1 mmol 2-nitroaniline or 2-4-dinitroaniline(CeH5N304) as secondary ligand to the bright red solution obtained as a result of mixing and turning the colour of the solution to brownish red, iii. refluxing the reaction mixture for 3 hours and then filtering it, and iv. crystallising the filtered brownish red powder product and drying it under vacuum.

[0052] Said method is carried out in a single container and is an easy and fast method. The substances are added to a single reaction flask in order, then the resulting solution is waited and the crystals are isolated. Since there are no steps such as filtering, separation, evaporation, transferring to a separate container, isolating and treating with another material during the synthesis, our synthesis is a one-pot synthesis method. The synthesised structures can be easily separated in the crystal structure and their solubility is high.

[0053] In the method of the invention, while the compound of Formula 1 (N1 , N4- bis(salicylidene)-S-methyl-isothiosemicarbazidato-Nickel(ll).2-nitroaniline) is synthesised in the case that secondary ligand mentioned in the process step (ii) is 2- nitroaniline, when the secondary ligand is 2-4 dinitroaniline, the compound of Formula 2 (N1 , N4-bis(salicylidene)-S-methyl-isothiosemicarbazidato-Nickel(ll).2,4- dinitroaniline) is synthesised.

[0054] Complex I was prepared by the reaction of 2-hydroxy-benzaldehyde-S-methyl- isothiosemicarbazone, 2-hydroxy-benzaldehyde, 2-nitroaniline and NiCl2.6H2O. The synthesis of Complex I is shown in Reaction 1 given below.

[0055] Reaction 1

[0056] Complex II was prepared by the reaction of 2-hydroxy-benzaldehyde-S-methyl- isothiosemicarbazone, 2-hydroxy-benzaldehyde, 2-4-dinitroaniline and NiCl2.6H2O. The synthesis of Complex II is shown in Reaction 2 given below.

[0057] Reaction 2

[0058] Elemental analysis, IR spectroscopy,1H-NMR spectroscopy, UV-Vis Spectroscopy and X-ray diffraction methods were applied for the synthesised nickelophilic metal complexes. The DFT (Density Functional Theory) method was used for theoretical calculations using the crystal structures of the complexes. The potential semiconductor and NLO (Non-linear optical) material properties of the complexes were theoretically proven by performing absorbance, transmittance, and reflectance measurements of the samples. In addition, the electrochemical properties of the sample solution were investigated. The solid-state structures of Complex I and Complex II were precisely determined by single crystal X-ray analysis. The molecular structures of Complex I and Complex II are shown by Formula 1 and Formula 2, respectively, while the selected experimental and theoretical geometric parameters are given in Table 1.

[0059] Table 1. Bond Lengths and Bond Angles of Complex I and Complex II.

[0060] Parameters Complex I Complex II

[0061] X-rav DFT X-rav DFT

[0062] Bond Lengths (A)

[0063] Nil— 01 1.830(6) 1.847 1.835(4) 1.849

[0064] Nil— 02 1.851 (6) 1.841 1.838(4) 1.845

[0065] Nil— N1 1.833(7) 1.846 1.817(4) 1.838

[0066] Nil— N3 1.818(8) 1.859 1.821 (4) 1.852

[0067] S1-C8 1.722(12) [1.721 (12)] 1.759 1 .755(9) [1 .755(9)] 1.758

[0068] S1-C9 1.760(8) [1.759(8)] 1.809 1 .854(4) [1 .856(4)] 1.809

[0069] O1-C1 1.315(10) 1.301 1.310(6) 1.305 O2-C16 1.304(10) 1.285 1.332(7) 1.289

[0070] N1-C7 1.268(9) 1.306 1.299(5) 1.306

[0071] N1-N2 1.297(10) [1.298(10)] 1.371 1 .356(8) [1 .356(8)] 1.372

[0072] N2-C8 1.265(12) [1.264(12)] 1.295 1 .274(8) [1 .274(8)] 1.294

[0073] N3-C8 1 .522(12) [1 .524(12)] 1 .391 1 .461 (10) [1 .462(10)] 1 .393

[0074] N3-C10 1.321 (10) 1.319 1.315(5) 1.318

[0075] O3-N5 1.221 (11 ) 1.235 1.204(6) 1.220

[0076] O4-N5 1.222(10) 1.218 1.198(6) 1.218

[0077] O5-N6 - - 1.215(6) 1.215

[0078] O6-N6 - - 1.220(6) 1.230

[0079] N4-C17 1.347(13) 1.347 1.325(6) 1.337

[0080] N5-C22 1.428(13) 1.442

[0081] N5-C20 - - 1.453(7) 1.453

[0082] N6-C22 - - 1.462(7) 1.449

[0083] Bond Angles (°)

[0084] N1— Nil— N3 83.4(4) 83.14 83.3(2) 83.24

[0085] N1— Nil— 01 96.5(3) 94.99 96.20(17) 95.17

[0086] N3— Nil— 01 179.1 (3) 178.04 178.08(16) 178.40

[0087] N1— Nil— 02 176.8(3) 177.87 178.58(18) 178.29

[0088] N3— Nil— 02 93.4(3) 94.81 95.39(17) 95.09

[0089] 01— Nil— 02 86.7(3) 87.07 85.16(18) 86.50

[0090] C8-S1-C9 101.5(5) [101.6(5)] 100.19 100.3(4) [100.2(4)] 100.17

[0091] C7-N1-N2 112.0(8) [108.3(8)] 116.53 111 .1 (5) [110.0(5)] 116.18

[0092] N1-N2-C8 108.1 (11 ) [108.1 (11 )] 110.77 104.2(8) [104.2(8)] 110.65

[0093] N2-C8-N3 119.9(11 ) [119.8(11 )] 119.12 123.6(9) [123.6(9)] 118.86

[0094] N2-C8-S1 122.6(10) [122.6(10)] 120.66 119.1 (9) [119.0(9)] 120.83

[0095] N3-C8-S1 117.5(8) [117.6(8)] 120.22 117.3(6) [117.3(6)] 120.31

[0096] C8-N3-C10 124.0(8) [127.9(7)] 123.01 124.8(5) [125.9(5)] 122.73

[0097] O3-N5-O4 119.9(10) 122.53 122.7(5) 124.90

[0098] O5-N6-O6 - - 123.3(5) 123.34

[0099] O3-N5-C22 119.6(11 ) 118.71

[0100] O4-N5-C22 120.5(11 ) 118.75

[0101] O3-N5-C20 - - 119.3(5) 117.25

[0102] O4-N5-C20 - - 117.9(6) 117.85

[0103] O5-N6-C22 - - 119.0(5) 118.46

[0104] O6-N6-C22 - - 117.6(5) 118.20

[0105] In the asymmetric unit of the co-crystal compounds, there is a mononuclear nickel complex. This is a 2-nitroan iline molecule in complex I and a 2,4-dinitroan iline molecule in complex II. The complex part of the compounds is the same and the structure of these compounds consists of an S-Methyl-N1 , N4-bis(salicylidene)- isothiosemicarbazide ligand and a Ni" metal centre. As shown in Figure 1 and Figure 2, the central Ni atom is tetra-coordinated in a square-planar geometry. The two phenolato oxygen atoms and two azomethine nitrogen atoms of the doubly deprotonated ONNO tetradentate Schiff-base ligand are located at the corners of the square plane. The four-coordinate geometry index (T4)

[0001] was found to be, both experimentally and theoretically, 0.03 for complex I and 0.02 for complex II and forms a slightly distorted square-planar geometry around the metal atom. The bond distances between the metal and donor atoms are in a narrow range from 1 .818(8) to 1 .851 (6) A for complex I and 1.817(4) to 1.838(4) A for complex II. The metal-ligand bond distances were calculated in the range of 1 .841 -1 .859 A for complex I and 1 .838-1 .852 A for complex II. However, the coordination bond distances are typical for the corresponding square-planar Ni complexes [2-5]. The trans angles ranging from 176.8(3) to 179.1 (3)° and the cis angles ranging from 83.3(2) to 96.5(3)° confirm the disruption of coordination around the nickel ions. The change values in cis and trans angles in the theoretical structures vary between 83.14 and 95.17° and 177.87 and 178.40°, respectively. When the bond lengths in free and coordinated isothiosemicarbazide ligands are compared, it is seen that C— O bonds are shortened with the formation of Ni— O bonds, while there are small changes of 0.01 -0.03 A in other bonds.

[0106] When the bond lengths in free and coordinated isothiosemicarbazide ligands are compared, it is seen that C— O bonds are shortened with the formation of Ni— O bonds, while there are small changes of 0.01 -0.03 A in other bonds.

[0107] The agreement between the calculated (DFT geometries) and experimentally determined X-ray structures is 0.083 and 0.052 A in Complex I and 0.082 and 0.061 A in Complex II for the complex and organic parts of the co-crystals, respectively, and the root mean square deviation (RMSD) values are excellent.

[0108] The supramolecular properties of the compounds are also similar. In their molecular structures, the intramolecular N— H— O contact within the organic molecule forms a six- member ring with the graphic set descriptor S(6) [6] [Figure 1 and Figure 2], In addition, the organic part is connected to the complex part by two intermolecular N— H— O hydrogen bonds (Figure 9) and forms a ring. In addition, the crystal structures, and the complex parts of the crystal compound form centrosymmetric pairs where the six-member chelate rings are connected to each other via TT—TT stacking interactions with a geometric centre of 3.377(4) A in Complex I and 3.310(3) A in Complex II. In this arrangement, the Ni---Ni distance is 3.328(2) A in Complex I and 3.2524(11 ) A in Complex II (Figure 4, Figure 5, 6). Finally, each centrosymmetric pair interacts with a neighbouring pair via weaker TT—TT interactions, forming a zig-zag motif (Figure 9). In Complex I, this linkage is provided by a 3.567(5) A [3.624(6) A] centroid-to-centroid interaction between benzene and the five-member chelate rings and a 3.731 (4) A centroid-to-centroid interaction between the six-member chelate rings. In the case of Complex II, a 3.635(3) A centre-to-centre interaction between benzene and the six- member chelate rings is responsible for the linkage between neighbouring centrosymmetric (centre-symmetric) pairs (Figure 10).

[0109] Table 2. Hydrogen Bond Geometry for Complex I and Complex II

[0110] Complex I

[0111] N4— H4A 'O3 0.86 2.04 2,636(12) 126

[0112] N4— H4B 'O2 0.86 2.30 3,102(1 1 ) 156

[0113] N4— H4B 'O1 0.86 2.48 3,177(10) 139

[0114] Complex II

[0115] N4— H4A 'O6 0.86 2.01 2,613(6) 127

[0116] N4— H4B 'O2 0.86 2.25 3,050(6) 155

[0117] N4— H4B 'O1 0.86 2.40 3,054(6) 133

[0118] FT-IR analyses of the starting material, complex I and complex II were performed. When these analyses were examined, uaSym (NH), uSym (NH) and 5 (NH2) vibrations were observed at 3458, 3278 and 1635 cm-1peaks in the IR spectrum of the starting material, respectively. It was expected that these peaks would disappear in the IR spectrum of the complex due to chelation and were calculated as 3534, 3421 and 1635 cm-1, respectively. However, the peaks observed at 3479, 3302 cm-1for complex I and 3449, 3332 cm-1for complex II are the uaSym (NH) and uSym (NH) vibrations of 2- nitroaniline and 2,4-dinitroaniline, respectively. These peaks are predicted in the theoretical spectrum at 351 1 and 3326 cm-1for Complex I and 3502 and 3296 cm-1for Complex II, respectively.

[0119] While the imine peak of the starting material is observed at 1617 and 1602 cm-1, these vibrations are theoretically observed at 1644 and 1599 cm-1, respectively. After chelation, a new sharp intensity band is observed in the range of 1625-1584 cm-1, which belongs to a new imine group (N4=C) originating from the condensation of the thioamide nitrogen (N4) and the second aldehyde. The azomethine stretching vibration bands observed at 1604, 1599 and 1578 cm-1in the spectrum of complex I and at 1625, 1606, 1584 cm-1in the spectrum of complex II appear in the theoretical spectrum at 1612, 1596 and 1557 cm-1for complex I and 1611 , 1596 and 1558 cm-1for complex II, respectively. The calculated peaks at 1342 and 1312 cm-1for complex I and 1337 and 1308 cm-1for complex II are C— 0 vibrations observed at 1140, 1121 cm-1for complex I and 1160, 1 123 cm-1for complex II, respectively, in the FT-IR spectra. The C-N stretching absorptions observed at 1328 and 1256 cm-1and the -NO2 (uaSym and Usym) peaks observed at 1540 and 1388 cm-1for C— NH2 (aniline) are related to the nitroaniline group. These bands are recorded at 1480, 1395, 1600 and 1353 cm-1for Complex I and 1484, 1404, 1612 and 1379 cm-1for Complex II in the theoretical spectrum, respectively.

[0120] UV-Vis analyses of the starting material, complex I and complex II were performed. When the UV-Vis spectra of the starting material and complexes are examined, it is seen that they are recorded between 200 and 800 nm. UV-Vis spectra of the starting material in CHCh show five bands at 239.5, 293, 304.5, 333.5, 346.5sh nm, which can be assigned to the TT-TT*, n-o* transitions of the aromatic ring, and the n-ir* transitions of the azomethine group on phenol, amine, thioether and thiosemicarbazone. In the UV-Vis spectra of Complex I, the TT-TT* transitions of intramolecular charge transfer were recorded at 240.5, 281 and 300 nm, and the n-rr* transitions of the azomethine group were recorded at 322.5 nm. The charge transfer transitions from ligand to metal and d-d transitions were recorded at 395 and 549.5 nm. The UV-Vis spectrum of Complex II was similar to Complex I, with bands observed at 227, 242.5, 302.5, 326, 393, 475.5 and 549.5 nm, respectively. The observed bands at 228, 280 and 474 nm were assigned to the nitro-substituted-aniline in the crystal structure. [7] The bands at 240.5, 300, 322.5, 395 and 549.5 nm were attributed to TT-TT*, n-rr* charge transfer and d-d transitions. When the starting material was coupled to a salicylaldehyde, a conjugated chelate structure with a rr-electron system was formed. Thus, both the increase of conjugation and the coordination of the chelate to the metal atom via the azomethine groups caused the absorptions to shift to a longer wavelength.

[0121] After the absorption spectra of the compounds were calculated by the time-dependent density functional theory (TD-DFT) method, the main contributions of the molecular orbitals (HOMO: H, LUMO: L) to the electronic transitions were determined by the GaussSum program [8]. TD-DFT calculations 234 nm [main contributions: H^L+1 (%64), H-3— >L (%13) and H-4^L (%10)], 247 nm [main contributions: H-3^L (%83) and H^L+1 (%14)], 289 nm [main contribution: H-1^L (%91 )] and for the starting thiosemicarbazone compound 331 nm [main contribution: H^L (%97)], for Complex I 485 nm [main contribution: H^L (%73) and H-1 ^L (%24)] and for Complex II 486 nm [main contribution: H^L (%97)]. In addition, the energy separation between H and L was found to be 3.75 eV for the starting material, 2.32 eV for Complex I and 2.62 eV for Complex II.

[0122] When the solvent effects on the UV / vis absorption spectra were examined, the UV-Vis spectra of the starting material and the complex were recorded between 200 and 800 nm. In the UV-Vis spectrum of the starting material in CHCh, five bands were observed at 239.5, 293, 304.5, 333.5, 346.5sh, which can be assigned to the TT-TT* transition of phenol, to aromatic ring, and to n-o* and n-rr* transitions of azomethine and thioamide groups of thiosemicarbazone.

[0123] In the UV-Vis spectrum of the complex, the TT-TT* transitions of phenyl rings were observed at 241 .5 nm. The n-rr* transitions of the thioamide group were recorded at 327.50 nm. The charge transfer transitions from the ligand to the metal and the d-d transitions were recorded at 552.50 nm.

[0124] The relationship between complex II and the solvent molecules was optically investigated with UV-Vis spectra in seven solvents consisting of polar aprotic and protic solvents with different polarities at room temperature. In addition to the solvent difference, the behaviours of complex II with solvents were investigated at different temperatures and under UV irradiation. To this end, the solutions were induced at - 10DC and 70DC temperatures and under 366 nm light for 30 minutes.

[0125] The complexes were dissolved in the most commonly used solvents DMSO, DMF, isopropylalcohol (i-PrOH), methanol (MeOH), THF, dichloromethane (DCM), and chloroform to prepare solutions at 50 pM concentration.

[0126] The changes in absorptions in the 215-265 nm and 315-350 nm ranges that stand out in the spectra are related to charge transfer transitions. In addition, among these, DMSO showed d-d transitions with a molar extinction coefficient £ in the range of 600- 800 nm: (400 M ’1cnr1Due to changes in electron distribution, donor-acceptor interactions caused the formation of new energy transitions in the spectrum.

[0127] In the UV-Vis spectra recorded at room temperature, it was noticed that the absorption band in the region of 315-350 nm showed a bathochromic shift and an increase in optical density with increasing solvent polarity. In the spectra of DMSO and DMF solutions, the transition at 348 and 345 nm, respectively, was observed with decreasing intensity and lower frequency in the spectra of other solutions. This band did not appear clearly in CHCh and CH2CI2 solutions.

[0128] The main absorption peak showed a spectral shift towards shorter wavelengths in the spectra of other solutions compared to the peak at 264 nm in the aprotic solvent DMF. The band character of this transition, except for the width, is the same as in aprotic solvents DMSO and THF. Said three solvents have the lowest a value, which refers to the hydrogen bond donating ability (HBD) of the solvent. In other cases, the shift of the main peaks to lower wavelengths is consistent with the increase in the HBD of the solvents. As a result, it was observed that both NO2 and NH2 groups on the co-ligand of the complex structure can interact with the solvent molecules. Probably, specific solvent-solute interactions through hydrogen bonding produced different absorption shifts in the spectra of the studied solvents. The lone pair on the nitrogen atom can interact with solvent molecules.

[0129] Comparison of absorption spectra of Complex I and II in chloroform is given in Figure 7. Absorption spectrum of Complex II in different solvents (DMF, DMSO, MeOH, THF, i-PrOH, DCM, CHCh) is given in Figure 8. The behaviours of Complex I in DMF and DMSO under cold (0°C) and solvent boiling temperature conditions were investigated and absorption spectra were taken and given in Figures 11 and 12.

[0130] When nonlinear optical properties are examined, a and [3 values calculated for complex I and complex II are 59.92 A3 and 52.33x1 O’31cm5 / esu for complex I, and 60.02 A3 and 104.12X10’31cm5 / esu for complex II, respectively. Urea and p-nitroaniline are prototype molecules used in the study of NLO properties of molecular systems. Therefore, they are used as reference molecules in NLO studies, a and [3 values calculated at the same level for urea and p-nitroaniline are 3.88 A3 and 7.71 x10-31 cm5 / esu, and 12.85 A3 and 96.21 x10-31 cm5 / esu, respectively. According to these values, complex I and complex II appear to be good candidates for NLO materials.

[0131] Determination of band gaps of synthesised complexes was carried out by diffuse reflection spectra. Optical diffuse reflection spectra of Complex II and Complex I showed reflection at long wavelengths and exhibited absorption edges of 3.55 eV and 2.42 eV in UV-vis spectrum, respectively. When experimental optical properties were examined, determination of band gaps of synthesised complexes was carried out by diffuse reflection spectra. Tauc relation is used to calculate the band gap values using equation (1).

[0132] (ahv)n= A(hv- Eg) (1 )

[0133] Here A is the band edge parameter and n value determines the nature of optical transition (n = indicates direct transition and n = 2 indicates indirect transition). The direct energy gap is determined by plotting a graph between (c / iv)2and / iv, and extrapolation towards (c / iv)2= 0 gives the direct band gap values of different concentrations. HOMO-LUMO energy gap (band gap) is the physical properties of a molecule that can create potential for the interaction of electrons in energy levels, the smaller the band gap value, the easier it is to excite electrons, thus the higher the nature of photosensitivity is.

[0134] REFERENCES

[0135] [1] L. Yang, D R. Powell, R.P. Houser, Dalton Trans. 9 (2007) 955-964. https: / / doi.Org / 10.1039 / B617136B

[0136] [2] V.B. Arion, V.Ch. Kravtsov, J. I. Gradinaru, Y.A. Simonov, N.V. Gerbeleu, J. Lipkowski, J.-P. Wignacourt, H. Vezin, 0. Mentre, Inorg. Chim. Acta 328 (2002) 123-133. https: / / doi.Org / 10.1016 / S0020-1693(01 )00717-4

[0137] [3] Y. Kurt, A. Koca, M. Akkurt, B. Ulkuseven, Inorg. Chim. Acta 388 (2012) 148-156. https: / / d0i.0rg / l 0.1016 / j.ica.2012.03.023

[0138] [4] R. Takjoo, R. Centore, A. Akbari, M. Ahmadi, Polyhedron 80 (2014) 243-249. https: / / d0i.0rg / l 0.1016 / j. poly .2014.04.055

[0139] [5] P. Vijayan, P. Anitha, M. Rajeshkumar, P. Viswanathamurthi, P. Sugumar, M.N.

[0140] Ponnuswamy, Polyhedron 124 (2017) 77-85. https: / / doi.Org / 10.1016 / j.polv.2016.12.031

[0141] [6] J. Bernstein, R.E. Davies, L. Shimoni, N.L. Chang, Angew. Chem., Int. Ed. Engl. 34 (1995) 1555-1573. https: / / doi.Org / 10.1002 / anie.199515551

[0142] [7] Grammaticakis, P., Contribution a I'etude de I'absorption dans I'ultraviolet moyen et le visible des arylamines isomeres et de leurs derives N substitues (Premier memoire), Bull. Soc. Chim. Fr. Docum, 1951 , 18, 220-226

[0143] [8] N.M. O'Boyle, A.L. Tenderholt, K.M. Langner, J. Comp. Chem. 29 (2008) 839-845. https: / / d0i.0rg / l 0.1002 / jcc.20823

Claims

CLAIMS1. Nickelophilic thiosemicarbazone complex with chemical structure shown by formula X, showing semiconductor and nonlinear optical, solvatochromism, thermochromism properties, whereinFormula X it is selected from R= — H, — NO2.

2. A complex according to Claim 1 , wherein, irrthat case that R= H, it is the molecule shown by Formula 1 (N1 ,N4-bis(salicylidene)-S-methyl- isothiosemicarbazidato-Nickel(ll).2-nitroaniline.Formula 13. A complex according to Claim 1 , wherein, in “that case that R= NO2, it is the molecule shown by Formula 2 (N1 ,N4-bis(salicylidene)-S-methyl- isothiosemicarbazidato-Nickel(ll).2,4-dinitroaniline).Formula 24. A nickelophilic thiosemicarbazone complex according to claim 1 , wherein the melting temperature of C22HigN5NiO4S compound (Formula 1 ) is 188-189°C.

5. A nickelophilic thiosemicarbazone complex according to claim 4, wherein the C22HigN5NiO4S compound (Formula 1 ) comprises: C, 52.00%; H, 3.77; N, 13.78; S, 6.31 , by mass (%).

6. A nickelophilic thiosemicarbazone complex according to claim 5, wherein the IR spectrum of C22HigN5NiO4S compound (Formula 1 ) comprises 3479, 3302 (Aliphatic asymmetric and symmetric N-H stretching bands); 3157, 2948, 2869 (C=CH stretching bands), 1621 (6(N-H) ); 1604, 1599, 1578 (C=N); 1 140, 1 121 (C- O); 1543, 1345 (Aliphatic asymmetric and symmetric N-0 stretching bands); 697 (u(C-S)) peaks.

7. A nickelophilic thiosemicarbazone complex according to claim 6, wherein the1H NMR spectrum of CggH-igNsNiC S compound (Formula 1 ) comprises (DMSO-d6, 25°C, ppm): 8.52 (s, 1 H, CH=N4); 8.33 (s, 2H, NH2); 8.30 (s, 1 H, CH=N1 ); 7.93 (dd, 1 H, Jxy= 1 .34, Jxz= 8.72, x); 7. 74 (dd, 1 H, J= 1 .68, J= 8.05, d); 7.55 (dd, 1 H, J= 1 .68, J= 8.05, s); 7.45 (td, 1 H, J= 1 .68, J= 6.71 , J= 7.04, b); 7.37 (ddd, 1 H, J= 1 .34, J= 1 . 68, J= 6.71 , z); 7.33 (td, 1 H, J= 1 .68, J= 6.71 , J= 7.05, q); 7.00 (dd, 1 H, J= 1 .34, J= 8.72, w); 6.98 (d, 1 H, J= 8.73, p); 6.91 (d, 1 H, J= 8. 73, a); 6.71 (t, 1 H, J= 7.04, J= 7.72, c); 6.63 (t, 1 H, J= 7.04, J= 7.38, r); 6.59 (ddd, 1 H, J= 1.01 , J= 1 .68, J= 6.71 , y); 2.71 (s, 3H, S-CH3) peaks.

8. A nickelophilic thiosemicarbazone complex according to claim 7, wherein the UV- Vis spectrum of CggH NsNiC S compound (Formula 1 ) comprises (5.1 O’5M,CHCI3): ((A (£)) 227 (11000), 242.5 (18240), 302.5 (9180), 326 (8720), 393 (7600), 475.5 (2700), 549 (1560) peaks.

9. A nickelophilic thiosemicarbazone complex according to claim 1 , wherein the melting temperature of C22Hi8N6NiOeS compound (Formula 2) is 179-180°C.10.A nickelophilic thiosemicarbazone complex according to claim 9, wherein the C22Hi8N6NiOeS compound (Formula 2) comprises: C,47.12; H, 3.84; N, 15.08; S,5.29, by mass (%).

11. A nickelophilic thiosemicarbazone complex according to claim 10, wherein C22Hi8N6NiOeS compound (Formula 2) comprises 1625, 1606, 1584 v(C=N); 1160, 1123 v(C-O); 3449, 3332 v(-NH); 1540, 1388 v(-NO2) peaks.12.A nickelophilic thiosemicarbazone complex according to claim 10, wherein1H NMR spectrum of C22Hi8N6NiOeS compound (Formula 2) comprises (DMSO-d6, 25 C, ppm): 8.80 - 8.46 ( s, 2H, NH2); 8.77 (d, 1 H, J= 2.93, x); 8.50 (s, 1 H, CH=N4);8. 29 (s, 1 H, CH=N1); 8.14 (dd, J= 2.93, J= 9.76, 1 H, y); 7.74 (dd, J= 1 .46, J= 8.29, 1 H, d); 7.53 (dd, J= 1 .95, J= 8.59, 1 H, s); 7. 44 (ddd, J= 1 .47, J= 6.35, J= 8.3, 1 H, b); 7.29 (ddd, J= 1 .96, J= 6.84, J= 8.79, 1 H, q); 7.09 (d, 9.76, 1 H, z); 6.97 (d, J= 8. 29, 1 H, p); 6.89 (d, J=8.29, 1 H, a); 6.70 (ddd, J=1 .46, J=7.32, J= 8.3, 1 H, c); 6.64 (t, J= 6.83, 1 H, r); 2.70 (s, 3H, S-CH3) peaks.

13. A nickelophilic thiosemicarbazone complex according to claim 12, wherein the UV- Vis spectrum of C22Hi8N5NiOeS compound (Formula 2) comprises (5.10-5 M, CHCI3): ((A (£)) 227 (11000), 242.5 (18240), 302.5 (9180), 326 (8720), 393 (7600), 475.5 (2700), 549 (1560) peaks.

14. Synthesis method of a nickelophilic thiosemicarbazone complex according to any one of the preceding claims, comprising the process steps of: i. mixing 2-Hydroxy-benzaldehyde-S-methyl-isothiosemicarbazone, (C9H11N13OS), 2-hydroxy benzaldehyde(C?H6O2) andNiCl2.6H2O (Nickel(ll) chloride hexahydrate) in ethanol (C2H6O), ii. adding 2-nitroaniline(CeH6N202) or 2-4-dinitroaniline(C6H5N304) as secondary ligand to the bright red solution obtained as a result of mixing and turning the colour of the solution to brownish red, iii. refluxing the reaction mixture and filtering, and iv. crystallising the filtered brownish red powder product and drying it under vacuum.15.The synthesis method of a nickelophilic thiosemicarbazone complex according to claim 14, comprising the steps of: i. mixing 1 -10 mmol of 2-Hydroxy-benzaldehyde-S-methyl- isothiosemicarbazone, 1 -3 mmol of 2-hydroxy benzaldehyde (C7H6O2) and 1 -10 mmol of nickel(ll) chloride hexahydrate (NiCl2.6H20) in methanol (C2H6O) for 1 -10 hours, ii. adding 2-nitroaniline(CsH6N20 or 2-4-dinitroaniline(CeH5N30) as secondary ligand to the bright red solution obtained as a result of mixing and turning the colour of the solution to brownish red, iii. refluxing the reaction mixture and filtering, and iv. crystallising the filtered brownish red powder product and drying it under vacuum.16.The synthesis method of a nickelophilic thiosemicarbazone complex according to claim 15, comprising the steps of: i. mixing 0.21 g, 1 mmol 2-Hydroxy-benzaldehyde-S-methyl- isothiosemicarbazone, 0.12 g, 1 mmol 2-hydroxy benzaldehyde and NiCI2.6H2O in 0.23 g, 1 mmol ethanol for 1 hour, ii. adding 0.14 g, 1 mmol 2-nitroaniline or 2-4-dinitroaniline as secondary ligand to the bright red solution obtained as a result of mixing and turning the colour of the solution to brownish red, iii. refluxing the reaction mixture for 3 hours and then filtering it, and iv. crystallising the filtered brownish red powder product and drying it under vacuum.

17. A method according to any one of claims 14-16, wherein in the case that the secondary ligand mentioned in the process step (ii) is 2-nitroaniline, the compound of formula 1 (N1 , N4-bis(salicylidene)-S-methyl-isothiosemicarbazidato-Nickel(ll).2-nitroaniline) is synthesised.

18. A method according to any one of claims 14-16, wherein in the case that the secondary ligand mentioned in the process step (ii) is 2-4 dinitroaniline, the compound of formula 2 (N1 ,N4-bis(salicylidene)-S-methyl-isothiosemicarbazidato- Nickel(ll).2,4-dinitroaniline) is synthesised.

19. Nickelophilic thiosemicarbazone complex synthesised by a method according to any one of claims 14-16.

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