Squarylium Dye Solubility via Asymmetric Functional Groups
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Solution Overview
Problem
Squarylium dyes have limited solubility, which restricts their applications due to low solubility in common solvents, especially in alcohols, where solubilities are less than 10 gm/L and often less than 1 gm/L, hindering their use in various applications.
Innovation Solution
A method involving the reaction of three or more amine bases with squaric acid or its derivatives to produce a mixture of squarylium dyes, increasing solubility by five or more times compared to the least soluble symmetric dye, and incorporating specific functional groups such as alkyl, arylsulfonate, and amine-based R groups to enhance solubility and photophysical properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If squarylium dyes are synthesized using conventional methods with limited functional groups, then the synthesis process is simple, but the solubility remains low (less than 10 gm/L in alcohols)
Solution Approach 1:
The patent applies parameter changes by systematically varying the R groups (alkyl, aryl, heteroaryl) and R' groups (carboxylate, sulfonate, phosphate) attached to the squarylium core structure. These chemical parameter modifications directly enhance solubility by introducing polar and ionizable functional groups that increase interaction with solvent molecules, transforming the dye from poorly soluble to highly soluble forms suitable for various applications.
Solution Approach 2:
The patent creates composite molecular structures by combining the squarylium core with multiple types of functional groups including carboxylates, sulfonates, phosphates, and various alkyl/aryl substituents. This composite approach integrates hydrophobic and hydrophilic components within the same molecule, achieving balanced solubility properties while maintaining the desired photophysical characteristics of the squarylium dye.
2Adaptability or versatility
If symmetric squarylium dyes are used, then the molecular structure is simple, but the solubility is limited and application range is restricted
Solution Approach 1:
The patent employs asymmetry by introducing different R and R' group combinations at various positions around the squarylium core, creating asymmetric molecular structures that break the symmetry of conventional squarylium dyes. This asymmetry prevents crystal packing that leads to low solubility and enables the dye to interact more effectively with various solvents and substrates, expanding application versatility.
Solution Approach 2:
The patent applies local quality by strategically placing specific functional groups at specific positions on the squarylium molecule. Different regions of the molecule are equipped with different functional groups (e.g., carboxylates at one position, sulfonates at another, alkyl chains at others) to optimize local interactions with solvents and substrates, thereby enhancing overall solubility and application performance without requiring complete structural redesign.
3Quantity of substance
If multiple amine bases are reacted with squaric acid to create dye mixtures, then solubility increases (5 or more times), but the mixture complexity increases
Solution Approach 1:
The patent merges multiple squarylium dye molecules with different R and R' group combinations into a single formulation or mixture. By combining dyes synthesized from different amine bases (such as dihydroindole, indole, carbazole derivatives) with various functional groups, the patent creates a synergistic mixture where each component contributes to overall solubility and performance, achieving 5 or more times improvement in solubility compared to individual symmetric dyes.
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 method significantly enhances the solubility of squarylium dyes, allowing for higher concentrations and broader application, including improved photophysical, thermal, and light stability, and enables their use in authentication and identification methods by increasing solubility up to 100 times that of individual isomers.
Implementation Method 1
Squarylium dyes, or squaraines, which were first reported in the 1960's, are a class of often-fluorescent dyes with peak absorption wavelength ranging from mid-visible into infrared wavelengths
Implementation Method 2
Squarylium dyes, or squaraines, which were first reported in the 1960's, are a class of often-fluorescent dyes with peak absorption wavelength ranging from mid-visible into infrared wavelengths
Data Source
AI summary
Squarylium dyes with improved design flexibility via functionalization thereof thereby yielding desirable photophysical, solubility, thermal stability, and/or light stability properties, for example. The resulting dyes are useful in optical filters and as fluorescent indicators, for example.