Aryl-Substituted Dithiolene Metal Complexes for Colorless IR Absorption
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Solution Overview
Problem
Current colorless infrared (IR) absorbers used in security printing and other applications face challenges with chemical and boiling water fastness, light stability, and colorlessness, particularly in high-end applications like banknote printing.
Innovation Solution
Development of specific metal complexes of dithiolenes with aryl or heteroaryl substituted imidazolidine-2-chalcogenone-4,5-dithione ligands, which provide enhanced chemical resistance, light stability, and heat stability while maintaining colorlessness, suitable for security printing and laser-welding of plastics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional IR absorbers are used in security printing, then IR absorption function is achieved, but visible coloration and poor chemical fastness occur
Solution Approach 1:
The patent modifies the chemical structure of dithiolene metal complexes by introducing specific aryl and heteroaryl substituents at positions 1 and 3 of the imidazolidine-2-chalcogenone-4,5-dithione ligand. This structural parameter change transforms the electronic properties of the complex, shifting the absorption maximum to the IR region (700-1200 nm) while minimizing visible absorption, thereby achieving both colorlessness and improved chemical fastness simultaneously
Solution Approach 2:
The invention creates composite molecular structures combining metal centers (Ni, Pd, Pt) with specifically substituted dithiolene ligands. The aryl and heteroaryl groups at positions 1 and 3 of the ligand work synergistically with the metal-dithiolene core to enhance chemical stability while maintaining optimal IR absorption properties and colorlessness
2Reliability
If existing IR absorbers are used, then IR absorption is achieved, but light stability and heat stability are insufficient
Solution Approach 1:
The patent optimizes the ligand structure by introducing aryl and heteroaryl substituents at positions 1 and 3, which changes the electronic distribution and bonding characteristics of the complex. This parameter change enhances the complex's resistance to photodegradation and thermal decomposition, improving light stability and heat stability while maintaining chemical stability
3Object-affected harmful factors
If conventional dithiolene complexes are used, then IR absorption is achieved, but colorlessness is compromised
Solution Approach 1:
The patent precisely adjusts the substitution pattern on the dithiolene ligand, placing aryl and heteroaryl groups at positions 1 and 3. This parameter change modifies the HOMO-LUMO energy gap and electronic transitions, shifting absorption to the IR region while minimizing visible absorption, thereby achieving superior colorlessness without compromising IR absorption performance
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The new metal complexes exhibit excellent fastness to chemicals, boiling water, and light, ensuring minimal visible absorption in the visible spectrum, making them ideal for high-end applications such as banknote printing and IR-readable bar codes.
Implementation Method 1
an infrared absorbing material that comprises transition element atoms or ions whose infrared absorption is a consequence of electronic transitions within the d-shell of the transition element
Data Source
AI summary
The present invention relates to the use of specific metal complexes of dithiolenes with aryl or heteroarylsubstituted imidazolidine-2-chalcogenone-4,5-dithione ligands as colourless IR absorbers.