Radiation Laboratory and Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, Indiana 46556, USA.
J Phys Chem A. 2010 Mar 4;114(8):2744-50. doi: 10.1021/jp9118887.
The photochemical and redox properties of two newly synthesized tetrahydroquinoxaline-based squaraine dyes (SQ) are investigated using femto- and nanosecond laser flash photolysis, pulse radiolysis, and cyclic voltammetry. In acetonitrile and dichloromethane, these squaraines exist as monomers in the zwitterionic form (lambda(max) approximately 715 nm, epsilon(max) approximately 1.66 x 10(5) M(-1) cm(-1) in acetonitrile). Their excited singlet states ((1)SQ*) exhibit a broad absorption band at 480 nm, with singlet lifetimes of 44 and 123 ps for the two dyes. Both squaraines exhibit poor intersystem crossing efficiency (Phi(ISC) < 0.001). Their excited triplet states ((3)SQ*), however, are efficiently generated by triplet-triplet energy transfer using triplet excited 9,10-dibromoanthracene. The excited triplet states of the squaraine dyes exhibit a broad absorption band at ca. 560 nm (epsilon(triplet) approximately 4.2 x 10(4) M(-1) cm(-1)) and undergo deactivation via triplet-triplet annihilation and ground-state quenching processes. The oxidized forms of the investigated squaraines (SQ(*+)) exhibit absorption maxima at 510 and 610 nm.
研究了两种新合成的四氢喹喔啉基方酸染料（SQ）的光化学和氧化还原性质，使用飞秒和纳秒激光光解、脉冲辐射和循环伏安法进行研究。在乙腈和二氯甲烷中，这些方酸以两性离子形式（lambda(max)约为 715nm，epsilon(max)约为 1.66 x 10(5) M(-1) cm(-1) 在乙腈中）存在为单体。它们的激发单线态 ((1)SQ*) 表现出 480nm 处的宽吸收带，两种染料的单线态寿命分别为 44 和 123ps。两种方酸的系间窜越效率都很差（Phi(ISC) < 0.001）。然而，它们的激发三重态 ((3)SQ*) 通过三重态激发 9,10-二溴蒽的三重态-三重态能量转移有效地产生。方酸染料的激发三重态在约 560nm 处表现出宽吸收带（epsilon(triplet)约为 4.2 x 10(4) M(-1) cm(-1))，并通过三重态-三重态湮灭和基态猝灭过程失活。所研究的方酸的氧化形式（SQ(*+)) 在 510nm 和 610nm 处表现出最大吸收。
