A luminescent n-heterocyclic chalcogenone complex and a process for preparation thereof

Abstract

The present disclosure discloses a luminescent N-heterocyclic chalcogenone complex having light-emitting properties and exhibiting air stability. The complex emits green emission at a wavelength in the range of 520 – 550 nm. The present disclosure also reveals a process for preparing the N-heterocyclic chalcogenone with ease of bulk synthesis and short reaction time. Ref. Figure 1

Description

FIELD OF THE INVENTIONThe present disclosure relates to the field of optoelectronic devices. Particularly, the present disclosure relates to a chemical complex showing light-emitting properties for application in light-emitting diodes (LEDs). More specifically, the present disclosure relates to N-heterocyclic chalcogenone complexes and their method for preparation. BACKGROUND OF THE INVENTIONOrganic light-emitting diodes (OLEDs) use a variety of luminous metal complexes as emitters. However, precious metals like ruthenium, iridium, osmium, and platinum heavily dominate these emitters in OLED systems. In recent years, there has been considerable advancement in developing multifunctional luminescent materials. In this regard, inorganic-organic hybrid materials and metal complexes with d10 electronic configurations have received a lot of interest. They have been extensively explored for their fascinating photophysical characteristics, mainly because their excited state energy levels remain unquenched. Non-precious metals like copper are especially appealing due to their clear economic and sustainability benefits. Copper(I) complexes are extensively studied for their potential applications in various fields, including organic light-emitting diodes, light-emitting electrochemical cells, biological sensors, molecular wires, non-linear optics, electrically conductive materials and thermochromic sensors. Therefore, a stable copper complex is required to replace the expensive metal complexes (Ir, Os, Pt) in the light-emitting research field. N-heterocyclic chalcogenone ligands analogs of NHC ligands have attracted a lot of interest due to the following: (i) a wide range of applications in material science, catalysis, and biomedical fields, (ii) they are good σ-donor and π-acceptor nature, (iii) excellent stability in the air, no need to store in argon atmosphere, (iv) large gram scale synthesis by following simple procedures, (iv) unlike NHC it can act as bridging ligand and can coordinate more than one metal. Most of the polymer complexes contain NHC and phosphine ligands; however, they are unstable. Overcoming this problem and making a stable copper(I) polymer complex is very challenging, with an emphasis on the design and synthesis of ligands, which are very important. Oleksandra Veselska et al. in a research paper titled as "Effect of the 1D / 2D dimensionality in copper and silver thiolate coordination polymers on their photophysical properties" discloses a series of four new copper and silver-thiolate, [M(m-SPhCO2R)]n (M = Cu, Ag and R = H, Me), coordination polymers showing that the hydrogen bonding between the carboxylic acids directs the formation of a 2D structure associated with poor photoemission, while the steric hindrance of the ester groups allows the assembly of a 1D network coupled with bright luminescence. However, the process of synthesis involved includes heating the reaction mixture at 120 °C for 24 hours in a sealed 20 mL vial and the resulting solid was subsequently purified by repeated washing with ethanol and acetone. Yue Wu et. al. in a research paper titled as "A super-stable Cu(i)-based polymer exhibiting thermally activated delayed fluorescence and water / acid-resistant properties" discloses a method of synthesis in which CuI (100.0 mg, 0.525 mmol) and 2,6-bis(diphenylphosphino)pyridine (117.5 mg, 0.263 mmol) were dissolved in anhydrous acetonitrile (30 mL) under argon. The mixture was stirred at room temperature for 10 min, heated to 100 °C, over 2 h, maintained at this temperature for 24 h, and then cooled to 25 °C, over 6 h to afford bright yellow flake-like crystals for photophysical applications. However, this synthesis method of these polymers takes more time and require argon atmospheres to complete these reactions.Therefore, there exists a need in the art to develop a new highly luminescent Cu(I)-N-heterocyclic chalcogenone polymer complexes that are air-stable in nature with utilisation in light-emitting applications.OBJECTIVE OF THE INVENTIONThe objective of the present disclosure is to provide a luminescent N-heterocyclic chalcogenone complex with light-emitting properties.Another objective of the present disclosure is to provide a luminescent N-heterocyclic chalcogenone complex that is air-stable.Still another objective of the present disclosure is to provide a luminescent N-heterocyclic chalcogenone complex that emits a greenish color emission.Yet another objective of the present disclosure is to provide a process for preparing a luminescent N-heterocyclic chalcogenone complex.These and other objects and advantages of the present subject matter will be apparent to a person skilled in the art after consideration of the following detailed description, taking into consideration accompanying drawings in which preferred embodiments of the present subject matter are illustrated.SUMMARY OF THE INVENTIONAn aspect of the present disclosure provides a luminescent N-heterocyclic chalcogenone complex having the chemical structure formula 1, Formula 1wherein X is selected from the group consisting of PF6, BF4, and ClO4.Another aspect of the present disclosure provides a process for preparing a complex having a chemical structure of Formula 1 comprising the steps of, (i). dissolving 3,3'-(butane-1,4-diyl)bis(1-(pyridin-2-yl) 2H-imidazole-2-thione), [Cu(CH3CN)4]X in CH3CN solvent to obtain a mixture of solution, (ii). stirring the solution of step (i) at room temperature to obtain a reaction mixture, and (iii). drying the reaction mixture of step (ii) under vacuum and washing with a solvent mixture to obtain a complex having the chemical structure formula 1: Formula 1wherein X is selected from the group consisting of PF6, BF4, and ClO4. These and other aspects of the disclosed subject matter, as well as additional novel features, will be apparent from the description provided herein. The intent of this summary is not to provide a comprehensive description of the claimed subject matter but rather to provide a short overview of some of the subject matter's functionality. Other systems, methods, features, and advantages provided here will become apparent to one with skill in the art upon examination of the following figures and detailed description. It is intended that all such additional systems, methods, features, and advantages included within this description be within the scope of any claims.BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGSThe illustrated embodiments of the subject matter will be best understood by reference to the drawings. The following description is intended only by way of example, and simply illustrates certain selected embodiments of composite and processes that are consistent with the subject matter as claimed herein, wherein:Figure 1 illustrates (i) the Fourier Transform Infrared Spectroscopy (FT-IR) spectrum of complex 1; (ii) the Fourier Transform Infrared Spectroscopy (FT-IR) spectrum of complex 2; (iii) the Fourier Transform Infrared Spectroscopy (FT-IR) spectrum of complex 3.Figure 2 illustrates (i) experimental (Exp) and simulated (Simu) Powder XRD pattern of 1; (ii) experimental (Exp) and simulated (Simu) Powder XRD pattern of 2; (iii) experimental (Exp) and simulated (Simu) Powder XRD pattern of 3;Figure 3 illustrates (i) Single crystal X-ray Diffraction (XRD) structure of 1, hydrogen atoms are omitted for clarity; (ii) Single crystal X-ray Diffraction (XRD) structure of 2, hydrogen atoms are omitted for clarity; (iii) Single crystal X-ray Diffraction (XRD) structure of 3, hydrogen atoms are omitted for clarity;Figure 4 illustrates (i) Solid-state absorption spectra of complexes 1, 2, and 3; (ii) Solid-state fluorescence spectra of 1, 2, and 3; (iii) Single crystals image of 1, 2, and 3 under normal and UV light; (iv) Commission Internationale de L'Eclairage (CIE) 1931 diagram of compound 1, 2, and 3 in the crystalline state; Figure 5 illustrates (i) LED bulbs (410 nm, 3V) coated with compound 3; (ii) Emission spectrum of LED bulbs (410 nm, 3V) coated with complex 3; (iii) commission Internationale de L'Eclairage (CIE) 1931 coordinates of LED bulbs (410 nm, 3V) and LED bulbs (410 nm, 3V) coated with complexes 3;Figure 6 illustrates the single crystal X-ray Diffraction (XRD) structure of complexes 1-3; andFigure 7 illustrates the Thermogravimetric Analysis (TGA) graph of polymer complexes 1 and 2.DETAILED DESCRIPTION OF THE INVENTIONA detailed description of various exemplary embodiments of the disclosure is described herein. It should be noted that the embodiments are described herein in such detail as to communicate the disclosure. However, the amount of details provided herein is not intended to limit the anticipated variations of embodiments; on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the present disclosure. The terminology used herein is to describe particular embodiments only and is not intended to be limiting to the invention. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context indicates otherwise. It will be further understood that the terms "comprises" and / or "comprising", or "includes" and / or "including" or "has" and / or "having" when used in this specification specify the presence of stated features, regions, integers, steps, operations, elements, and / or components, but do not preclude the presence or addition of one or more other features, regions, integers, steps, operations, elements, components, and / or groups thereof.Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which example embodiments belong. It will be further understood that terms, e.g., those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.The term "further" is used in the embodiments and claims of the present application. The said term is a well-accepted term to narrow down any principal feature. Therefore, the person skilled in the art would clearly understand the scope of the said term in the context of the present disclosure.The present disclosure relates to a luminescent N-heterocyclic chalcogenone complex having the chemical structure formula 1: Formula 1wherein X is selected from the group consisting of PF6, BF4, and ClO4.In an embodiment of the present disclosure, a crystalline state quantum yield of the complex (Φ) is within the range of 0.2-1.8% with a lifetime of τavg = 0.7-1.4 μs.In another embodiment of the preset disclosure, the crystalline state quantum yield is defined as the efficiency with which a crystalline material, such as nanocrystals or organic crystals, converts absorbed photons into emitted photons (photoluminescence) or other desired processes.In another embodiment of the present disclosure, the complex is selected from a group consisting of[Cun(L1)n](PF6)n, [Cun(L1)n](BF4)n and [Cun(L1)n](ClO4)n, wherein L1 is 3,3'-(butane-1,4-diyl)bis(1-(pyridin-2-yl) 2H-imidazole-2-thione).In still another embodiment of the present disclosure, the complex [Cun(L1)n](PF6)n is referred to as complex 1, the complex [Cun(L1)n](BF4)n is referred to as complex 2 and the complex [Cun(L1)n](ClO4)n is referred to as complex 3 having the following chemical structure, Complex 1 Complex 2 Complex 3In still another embodiment of the present disclosure, a crystalline state of the complex shows green emission at a wavelength in the range of 520 - 550 nm.Another embodiment of the present disclosure provides a process for preparation of the complex having a chemical structure formula 1 comprising: i. dissolving 3,3'-(butane-1,4-diyl)bis(1-(pyridin-2-yl) 2H-imidazole-2-thione), [Cu(CH3CN)4]X in CH3CN solvent to obtain a mixture of solution;ii. stirring the solution of step (i) at room temperature to obtain a reaction mixture; andiii. drying the reaction mixture of step (ii) under vacuum and washing with a solvent mixture to obtain a complex having the chemical structure formula 1: wherein X is selected from the group consisting of PF6, BF4, and ClO4.In an embodiment of the present disclosure there is provided a process for preparation of the complex having the chemical structure formula 1, wherein the solvent is selected from the group consisting of acetone, chloroform, dichloromethane, hexane, or combinations thereof.In another embodiment of the present disclosure there is provided a process for preparation of the complex having the chemical structure formula 1, wherein an amount of 3,3'-(butane-1,4-diyl)bis(1-(pyridin-2-yl) 2H-imidazole-2-thione) is in the range of 0.2-0.8 g, [Cu(CH3CN)4]X is in the range of 0.10 - 0.20 g.In still another embodiment of the present disclosure there is provided a process for preparation of the complex having the chemical structure formula 1, wherein an amount of CH3CN is in the range of 1-5 mL for each reaction.In yet another embodiment of the present disclosure there is provided a process for preparation of the complex having the chemical structure formula 1, wherein the stirring is carried out for 20 minutes for each reaction at a temperature in the range of 25-35o C.In an embodiment of the present disclosure there is provided a process for preparation of the complex having the chemical structure formula 1, wherein the solvent mixture is acetone and hexane, and the ratio of the acetone and hexane is in the range of 1:1 to 1:2. The present disclosure pertains to the development of new air-stable one-dimensional luminescence copper(I) N-heterocyclic chalcogenone complexes for light-emitting purposes. Therefore, the present disclosure's complex is designed and synthesized stable ligands that are similar to NHC ligands. The present disclosure describes the detailed synthesis approach of unique cationic one-dimensional Cu(I)-N-heterocyclic chalcogenone complexes of 1, 2, and 3. In a solid crystalline state, complexes 1, 2, and 3 show green color emission at 528 nm for 1, 541 nm for 2, and 547 nm for 3 on excitation at 317 nm.Advantages of the present disclosure• The present disclosure is directed towards the synthesis of air-stable one-dimensional Cu(I)-N-heterocyclic chalcogenone complexes in which the reactions proceed quickly (within 20 minutes) to attain the products with ease of synthesis. • The present disclosure's complexes 1, 2, and 3, in their solid crystalline state, show green color emission at 528 nm for 1, 541 nm for 2, and 547 nm for 3 on excitation at 317 nm.• Emission spectra of the LED bulb (410 nm, 3V) coated with complex 3 was observed at 543 nm.• The synthesis process of the present disclosure leads to high product yield (89-92%).• The synthesis process of the present disclosure is feasible with bulk-scale synthesis.• The synthesis process of the present disclosure represents an acid-free reaction condition.EXAMPLESThe following examples are given by way of illustration, therefore, should not be construed to limit the scope of the disclosure.Example 1General Process for the preparation of a luminescent N-heterocyclic chalcogenone complex having the chemical structure Formula 1 Scheme 1The scheme 1 summarizes the process followed for the synthesis of the luminescent N-heterocyclic chalcogenone complex having the chemical structure formula 1.Synthesis of the N-heterocyclic chalcogenone complex 1 with PF6Dissolving 3,3'-(butane-1,4-diyl)bis(1-(pyridin-2-yl) 2H-imidazole-2-thione (0.5 g, 1.4 mmol), [Cu(CH3CN)4]PF6 (0.14 g, 1.4 mmol), and CH3CN (5 mL) in a 25 mL Schlenk tube and swirled at room temperature for 20 minutes to obtain a reaction mixture. The reaction mixture was dried under vacuum and then washed with acetone (10 mL) and hexane (10 mL) to obtain a yellow-colored complex which was isolated and crystallized in saturated CH3CN solution.The melting point of the complex 1 with PF6 is in the range of 266-268 °C and yield is 92 % (Based on [Cu(CH3CN)4]PF6. FT-IR (cm-1, ATR): u = 3123 (w), 3120 (w), 1594 (m), 1493 (m), 1471 (s), 1442 (s), 1225 (s), 1121 (m), 843 (vs), 658 (vs), 532 (m) cm-1. Scheme 2The scheme 2 summarizes the process followed for the synthesis of the N-heterocyclic chalcogenone complex 1 with PF6.Synthesis of the N-heterocyclic chalcogenone complex 2 with BF4Dissolving 3,3'-(butane-1,4-diyl)bis(1-(pyridin-2-yl) 2H-imidazole-2-thione (0.5 g, 1.4 mmol), [Cu(CH3CN)4]BF4 (0.14 g, 1.4 mmol), and CH3CN(5 mL) in a 25 mL Schlenk tube and swirled at room temperature for 20 minutes to obtain a reaction mixture. The reaction mixture was dried under vacuum and then washed with acetone (10 mL) and hexane (10 to 15 mL) to obtain a yellow-colored complex which was isolated and crystallized in saturated CH3CN solution.The melting point of the complex 2 with BF4 is 267-268 °C and yield is 89% ([Cu(CH3CN)4]BF4). FT-IR (cm-1, ATR): u = 3121 (w), 3118 (w), 1592 (m), 1582 (m), 1572 (m), 1493 (m), 1473 (s), 1442 (s), 1225 (s), 1121(m), 1034 (vs), 633 (vs), 532(m) cm-1. Scheme 3The scheme 3 summarizes the process followed for the synthesis of the N-heterocyclic chalcogenone complex 2 with BF4.Synthesis of the N-heterocyclic chalcogenone complex 3 with ClCO4Dissolving 3,3'-(butane-1,4-diyl)bis(1-(pyridin-2-yl) 2H-imidazole-2-thione (0.5 g, 1.4 mmol), [Cu(CH3CN)4]BF4 (0.14 g, 1.4 mmol), and CH3CN(5 mL) in a 25 mL Schlenk tube and swirled at room temperature for 20 minutes to obtain a reaction mixture. The reaction mixture was dried under vacuum and then washed with acetone (10 mL) and hexane (10 mL) to obtain a yellow-colored complex which was isolated and crystallized in saturated CH3CN solution.The yield of complex 3 with ClCO4 is 90 % ([Cu(CH3CN)4]ClO4). FT-IR (cm-1, ATR): u= 3121 (w), 3118 (w), 1593 (m), 1581 (m), 1573 (m), 1491 (m), 1474 (s), 1441 (s), 1226 (s), 1103 (m), 1034 (vs), 633 (vs), 532(m) cm-1. Scheme 4The scheme 4 summarizes the process followed for the synthesis of the N-heterocyclic chalcogenone complex 3 with ClCO4.Example 2Photophysical properties2.1 Fourier Transform Infrared SpectroscopyFT-IR spectroscopy was employed to confirm the presence of functional groups in all three complexes. FT-IR data were collected using a Bruker Alpha-P Fourier Transform spectrometer for complexes (1-3). Figure 1 shows (i) FT-IR spectrum of complex 1; (ii) FT-IR spectrum of complex 2; (iii) FT-IR spectrum of complex 3.In FT-IR spectra of complexes 1, 2, and 3, the observed C=S stretching frequency band was 1474 cm-1 for complex 1, 1473 cm-1 for complex 2, and 148 cm-1 for complex 3, which were very much consistent with the formation of complexes. A very strong and sharp stretching frequency band has been observed at 843 cm-1 for complex 1, 1034 cm-1 for complex 2, and 1103 cm-1 for complex 3 in the FTIR spectra, possibly due to non-coordinated PF6, BF4, and ClO4 ions, which confirmed the presence of the presence of functional groups in all three complexes.2.2 Powder X-ray DiffractionTo assess the purity of the bulk samples, powder X-ray diffraction (PXRD) analysis was performed for complexes 1, 2, and 3. The powder X-ray diffraction data were collected using a Rigaku Ultima IV. Figure 2. shows (i) experimental (Exp) and simulated (Simu) Powder XRD pattern of 1; (ii) experimental (Exp) and simulated (Simu) Powder XRD pattern of 2; (iii) experimental (Exp) and simulated (Simu) Powder XRD pattern of 3.The experimental PXRD patterns showed that all the complexes are crystalline in nature because sharp peaks were obtained in the PXRD pattern depicting excellent agreement with the simulated patterns for all three complexes, confirming the phase purity of the samples.2.3 Single crystal X-ray DiffractionThe formation of complexes 1, 2, and 3 was corroborated through single-crystal X-ray diffraction studies. Crystals 1-3 were mounted in a Bruker D8 Venture APEX-IV PHOTON diffractometer using the source MoKα (0.71073 Å) at 298 K.Figure 3. shows (i) Single crystal XRD structure of 1, hydrogen atoms are omitted for clarity; (ii) Single crystal XRD structure of 2, hydrogen atoms are omitted for clarity; (iii) Single crystal XRD structure of 3, hydrogen atoms are omitted for clarity.Suitable single crystals were obtained by slow evaporation from saturated acetonitrile solutions at room temperature; they crystallised in the monoclinic crystal system with space group C2 / c. Thus, it was confirmed that all complexes are isostructural in nature, and each central metal atom adopts a distorted tetrahedral geometry.2.4 UV-vis absorption spectraThe solid-state UV-vis absorption spectra of complexes 1, 2, and 3 were recorded at room temperature. Figure 4. shows (i) Solid-state absorption spectra of complexes 1, 2, and 3; (ii) Solid-state fluorescence spectra of 1, 2, and 3; (iii) Single crystals image of 1, 2, and 3 under normal and UV light; (iv) Commission Internationale de L'Eclairage (CIE) 1931 diagram of compound 1, 2, and 3 in the crystalline state.In the spectra, complex 1 shows two absorption bands at 268 nm and 317 nm; complex 2 exhibits three bands at 274 nm, 317 nm, and 412 nm; and complex 3 presents bands at 267 nm, 320 nm, and 413 nm. The absorption band around 317 nm, common to all three complexes, is assigned to an n->π* electronic transition. In contrast, the bands at shorter wavelengths, 268 nm (1), 274 nm (2), and 267 nm (3), are attributed to π->π* transitions, as illustrated in Figure 4(i). In the solid state, the emission spectra of complexes 1, 2, and 3 each display a single broad emission maximum. Upon excitation at 312 nm, complex 1 emits at 528 nm, complex 2 at 547 nm, and complex 3 at 541 nm, as shown in Figure 4(ii).The Commission Internationale de L'Eclairage (CIE) 1931 diagram, as shown in figure 4 (iv), that complexes 1, 2, and 3 yellowish-green emissions with CIE coordinates (x = 0.3308, y = 0.5738) for 1, (x = 0.3718, y = 0.5647) for 2, and (x = 0.3812, y = 0.5530) for 3 in the solid state. Photoluminescence quantum yields in Complexes 1, 2, and 3 were 1.5% (Φ), 1.8% (Φ), and 0.26% (Φ), respectively, with average lifetimes of 0.9 μs, 0.7 μs, and 1.4 μs. However, complexes 1, 2, and 3 do not emit in the solution state. Figure 4 (iii) shows crystal pictures of 1, 2, and 3 taken under handheld UV torch light (395 nm) and normal light, demonstrating the observed color variations of the complexes.2.5 Emission spectrum in LED bulbsTo assess the device‐level emissive behaviour of complex 3, 3V LEDs emitting 410 nm were fabricated using an acetonitrile solution containing poly(methyl methacrylate) (PMMA) films doped with complex 3. These coated LEDs were then examined by fluorescence spectroscopy at room temperature.Figure 5. shows (i) LED bulbs (410 nm, 3V) coated with compound 3; (ii) Emission spectrum of LED bulbs (410 nm, 3V) coated with complex 3; (iii) commission Internationale de L'Eclairage (CIE) 1931 coordinates of LED bulbs (410 nm, 3V) and LED bulbs (410 nm, 3V) coated with complexes 3.The emission spectra of the coated complex of 3 was 543 nm. when irradiated at a wavelength of 317 nm, the coated complex of 3 showed two distinct emission peaks, shown in figure 5 (ii), a lower wavelength peak at 410 nm that corresponds to the LED emission and a higher wavelength peak at 543 nm for complexes 3, which represents the emission from the respective complexes. Table 1 summarizes the peak wavelengths (λex and λem) of the solid samples and LED-coated bulbs, along with their CIE color space coordinates. The CIE diagram indicates that the solid samples of complexes 1, 2, and 3, comparable, emit a yellowish-green color, while the LED-coated bulb (3) produces a similar color to the solid-phase sample (λem = 543 nm) when excited at the characteristic wavelength.The comparable data of the crystalline solid-state samples and the PMMA-coated LED films indicate that the complexes retain their structural integrity and photophysical properties upon embedding in the polymer matrix. This demonstrates their stability, processability, and suitability for practical device applications.Table 1Example 3LED Demo ExperimentAn LED demonstration experiment was conducted to highlight the importance of complex 3 as a light-emitting material. In this experiment, compound 3 (15 mg) and PMMA (15 mg) were dissolved in 3 mL of CH3CN, and the resultant mixture was applied to an LED bulb (410 nm emitting, 3V). The coated LED bulb was then irradiated with 373 nm UV radiation, producing a yellowish-green color emission of 543 nm. This experiment shows that complex 3 has the intrinsic potential to act as a light-emitting material under UV light.Example 4Copper-sulphur stability in the synthesized complexesAccording to Pearson's HSAB theory, Cu(I) is a soft acid (due to its low charge density and polarizability), and sulphur donors are soft bases. Because of soft acid-soft base interactions, it will form a strong Cu(I) polymer complex [Inorg. Chem., 1992, 31, 2797-2800].The copper sulphur stability in copper polymer complexes can be determined through SCXRD analysis.Figure 6. shows single crystal XRD structure of complexes 1-3. The stable Cu-S bonds are typically in the 2.2-2.4 Å range for Cu(I)-S. In the present disclosure, all three polymer complexes (1-3), the Cu-S bond length lies in the range 2.22 to 2.25 Å. These are the shorter and stronger Cu(I)-S bond orders. These bond orders are significantly comparable with the reported Cu(I)-S bond, ranging from 2.22 to 2.29Å. Table 2 shows the observed Cu-S bond length of 1-3 in single-crystal XRD analysis [Chem. - Eur. J. 2025, 0, e202501113].Complex Cu-S Bond length1 2.254 Å2 2.254 Å3 2.220 ÅTGA was recorded using a TASDT Q600.Figure 7 shows the TGA graph of polymer complexes 1 and 2.TGA analysis revealed that the Cu(I) polymer exhibits thermal stability above 200 °C (Figure 7).Example 5Feasibility of Bulk SynthesisThe bulk synthesis of the present 1-3 polymer is feasible because the reaction involves readily available starting materials [(Cu (CH3CN)4] X, X = PF6, BF4, ClO4, and easy ligand preparation), is carried out under moderate temperatures and pressures, and does not require highly specialized equipment.Bulk purity of the sample was verified by PXRD analysis, where the experimental pattern closely matched the simulated one, confirming the successful bulk synthesis of the 1-3 polymer as described in Figure 2.It should be noted that the description and figures merely illustrate the principles of the present subject matter. It should be appreciated by those skilled in the art that conception and specific embodiment disclosed may be readily utilized as a basis for modifying or designing other structures for carrying out the same purposes of the present subject matter. It should also be appreciated by those skilled in the art that by devising various systems that, although not explicitly described or shown herein, embody the principles of the present subject matter and are included within its spirit and scope. Furthermore, all examples recited herein are principally intended expressly to be for pedagogical purposes to aid the reader in understanding the principles of the present subject matter and the concepts contributed by the inventor(s) to further the art and are to be construed as being without limitation to such specifically recited examples and conditions. The novel features which are believed to be characteristic of the present subject matter, both as to its organization and method of operation, together with further objects and advantages will be better understood from the following description when considered in connection with the accompanying figures. It will be further appreciated that functions or structures of a plurality of components or steps may be combined into a single component or step, or the functions or structures of one-step or component may be split among plural steps or components. The present invention contemplates all of these combinations. Unless stated otherwise, dimensions and geometries of the various structures depicted herein are not intended to be restrictive of the invention, and other dimensions or geometries are possible. In addition, while a feature of the present invention may have been described in the context of only one of the illustrated embodiments, such a feature may be combined with one or more other features of other embodiments, for any given application. It will also be appreciated from the above that the fabrication of the unique structures herein and the operation thereof also constitute methods in accordance with the present invention. The present invention also encompasses intermediate and end products resulting from the practice of the methods herein.

Claims

1. A luminescent N-heterocyclic chalcogenone complex having the chemical structure Formula 1: Formula 1 wherein X is selected from the group consisting of PF6, BF4, and ClO4.

2. The complex as claimed in claim 1, wherein a crystalline state quantum yield of the complex (Φ) is within the range of 0.2-1.8% with a lifetime of τavg = 0.7-1.4 μs.

3. The complex as claimed in claim 1, wherein the complex is selected from a group consisting of[Cun(L1)n](PF6)n, [Cun(L1)n](BF4)n and [Cun(L1)n](ClO4)n, wherein L1 is 3,3'-(butane-1,4-diyl)bis(1-(pyridin-2-yl) 2H-imidazole-2-thione ).

4. The complex as claimed in claim 1, wherein a crystalline state of the complex shows green emission at a wavelength in the range of 520 - 550 nm.

5. A process for preparing a complex having a chemical structure of Formula 1 comprising the steps of: i. dissolving 3,3'-(butane-1,4-diyl)bis(1-(pyridin-2-yl) 2H-imidazole-2-thione), [Cu(CH3CN)4]X in CH3CN solvent to obtain a mixture of solution; ii. stirring the solution of step (i) at room temperature to obtain a reaction mixture; and iii. drying the reaction mixture of step (ii) under vacuum and washing with a solvent mixture to obtain a complex having the chemical structure formula 1: wherein X is selected from the group consisting of PF6, BF4, and ClO4.

6. The process as claimed in claim 5, wherein the solvent is selected from the group consisting of acetone, chloroform, dichloromethane, hexane, or combinations thereof.

7. The process as claimed in claim 5, wherein an amount of 3, 3'-(butane-1,4-diyl)bis(1-(pyridin-2-yl) 2H-imidazole-2-thione) is in the range of 0.5-0.51 g, [Cu(CH3CN)4]X is in the range of 0.14 - 0.15 g.

8. The process as claimed in claim 5, wherein an amount of CH3CN is in the range of 1-5 mL for each reaction.

9. The process as claimed in claim 5, wherein the stirring is carried out for 20 minutes for each reaction at a temperature in the range of 25-35 °C.

10. The process as claimed in claim 5, wherein the solvent mixture is acetone and hexane, and the ratio of the acetone and hexane is in the range of 1:1-1:2.