含不同烷基链四苯基丁二烯衍生物的聚集诱导发光及力致变色性能

Series of 1,1,4,4-tetraphenylbuta-1,3-diene (TPB) derivatives, named TPB-COOCH₃-1~6 and TPB-COOH-1~6 containing different alkyl chains and polar substituents, were designed and synthesized by terminal alkyne dimerization and Pd-catalyzed cross-coupling, etc. The target compounds were characterized by ¹H nuclear magnetic resonance, ¹³C nuclear magnetic resonance, mass spectrum, Fourier transform infrared, from which satisfactory results to their molecular structures were obtained. They all have good thermal stabilities with high decomposition temperatures above 310 ℃ based on thermogravimetric analysis. Investigation of the photophysical properties indicated that the target compounds exhibited significant aggregation-induced emission (AIE) features with higher α_AIE (α_AIE=Φ_PL,solid/Φ_PL,solu) values of 20.5~49.6 for TPB-COOCH₃-1~6 and 14.4~26.3 for TPB-COOH-1~6, and their photoluminescence quantum yields in solid state (Φ_PL,solid) were determined as high as 71.3%~89.1% and 34.5%~73.2% for TPB-COOCH₃-1~6 and TPB-COOH-1~6, respectively. The different lengths of alkyl chains and the polarity of the other substituent had obvious effect on the regular molecular stacking of the target compounds when they were forced to aggregate or precipitate, which affects the intermolecular interaction and the restriction degree of the rotators, consequently influenced their AIE behavior in the tetrahydrofuran (THF)/H₂O mixtures. For the compounds TPB-COOCH₃-1~6 containing methyl esters and different alkyl chains, TPB-COOCH₃-3, which is with n-propyl, exhibited the most significant fluorescence enhancement (I/I₀=26.0) in the THF/H₂O mixtures. While, for TPB-COOH-1~6 containing -COOH and alkyl chains, TPB-COOH-6, which is with n-hexyl, had the maximum I/I₀ (I/I₀=15.7) due to the increase of hydrophilicity. Careful comparison revealed that the I/I₀ and Φ_PL,solid values of TPB-COOCH₃-1~6 were higher than those of TPB-COOH-1~6 containing same alkyl chains under the same measuring condition, mainly attributing to the interaction between the -COOH groups or between -COOH and the polar solvent molecules, which increasing the nonradiative energy decay and weakening fluorescence emission. Furthermore, the incorporation of bovine serum albumin (BSA) and human serum albumin (HSA) into TPB-COOH significantly enhanced the solid-state fluorescence emission, and the BSA and HSA also influenced the mechanochromic properties of the AIEgens containing -COOH. Especially, the fluorescence intensity increased obviously after grinding the doped system of TPB-COOH-2 and BSA, mainly because the existence and steric hindrance of BSA molecules weakened the π-π interaction of the planarized TPB-COOH-2 molecules, which effectively inhibiting the intramolecular rotation of benzene ring and reducing the nonradia tive energy loss.