Abstract
A series of 2,6-bis-styryl-4H-pyran-4-ylidene fragment containing glass-forming organic compounds with bonded amorphous phase promoting bulky triphenyl moieties through piperazine structural fragment [2-(2-(4-(bis(2-(trityloxy)ethyl)amino)styryl)-6-methyl-4H-pyran-4ylidene)malononitrile derivatives (DWK)-T dyes] in a form of (5,5,5-triphenylpentyl)piperazin-1-yl)styryl)-substituent attached to the 4H-pyran-4-yliden fragment in two-position have been synthesized and investigated as the potential light-amplification medium for organic solid-state lasers. DWK-T dye physical properties also depend on the structure of the other styryl-substituent attached to the 4H-pyran-4-ylidene backbone fragment in six-position. Thermal stability of synthesized dyes is above 312°C with the glass transitions from 97°C and up to 109°C. Obtained neat pure spin-cast films based on these compounds show photoluminescence with λmax in range from 672 to 695 nm, ASE λmax from 690 to 704 nm with ASE threshold values in range from 327 to 1091 μJ / cm2, which are mostly influenced by the nature of the electron transition characteristics of various four substituents in a 6-styryl-fragment. The proposed synthetic approach could be useful for obtaining chemically stable and covalently bonded bulky triphenyl group containing glassy dyes, while the synthetic design allows to acquire different nonsymmetric 2,6-bis-styryl-4H-pyran-4-ylidene fragment-containing compounds for red and infrared light-emitting and light amplification applications.
Highlights
Since Tang et al.[1] introduced the 4-(dicyanomethylene)-2-methyl-6-(4-dimethylaminostyryl)4H-pyran (DCM) laser dye, a great number of scientists around the world have been extensively studying the chemistry and physics of the mentioned dye
Spin-coated neat films based on mono-styryl- and symmetric 2,6-bis-styryl-DWK-type dyes showed significantly increased photoluminescence quantum yields (PLQY) and notably lower amplified spontaneous emission (ASE) threshold energies in comparison
Glass-forming bis-DWK-type compounds have been obtained according to the scheme shown in Fig. 1. 2-Styryl-substituted-6-methyl-4H-pyran-4-ylidene derivatives 4a, 4b, 4c, and 4e were
Summary
Since Tang et al.[1] introduced the 4-(dicyanomethylene)-2-methyl-6-(4-dimethylaminostyryl)4H-pyran (DCM) laser dye, a great number of scientists around the world have been extensively studying the chemistry and physics of the mentioned dye. With the conventional DCM dye.[8,9,10,11] the linking type of the bulky moieties via ether bonds is chemically unstable as de-trytilation may take place in slightly acidic conditions It results in crystallization of the amorphous neat films, which leads to the decrease in the PLQY and increase in the ASE threshold values of the light-amplification medium. To prevent these drawbacks, a series of 2,6-bis-styryl-4H-pyran-4-ylidene fragment containing glass-forming organic compounds with the chemically stable bonding of bulky triphenyl moieties through piperazine structural fragment in a form of 2-(5,5,5-triphenylpentyl)piperazin-1-yl)styryl)-substituent have been synthesized and investigated. Full preparation of dyes, obtained dye structural relation with their thermal, glass-forming, light-absorption, light-emitting, and ASE properties are discussed in this report
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