Wohl Christopher J, Kuciauskas Darius
Department of Chemistry, Virginia Commonwealth University, 1001 West Main Street, Richmond, Virginia 23284-2006, USA.
J Phys Chem B. 2005 Dec 1;109(47):22186-91. doi: 10.1021/jp053782x.
Merocyanine (MC) isomers that are formed after absorption of a UV photon by 1',3'-dihydro-1',3'-3'-trimethyl-6-nitrospiro[2H-1-benzopyran-2',2'-(2H)-indole] were studied. Several, predominantly TTC and TTT, merocyanine isomers are present in toluene solution ("T" and "C" indicate trans and cis conformations of the C-C bonds in the methine bridge). Excitation in the MC visible absorption band (at 490, 550, and 630 nm) with 100 fs laser pulses was used to study MC excited-state dynamics. Internal conversion on the picosecond time scale was found to be the dominant relaxation pathway. Excited-state isomerization reactions were also observed. Excitation at 630 nm (assigned to TTC isomer excitation) leads to formation of a third isomer (either CTC or CTT). Excitation at 490 nm (assigned to TTT isomer excitation) leads to more complex excited-state relaxation, including formation of two isomers: TTC (absorption at 600 nm) and CTC or CTT (absorption at 650 nm).
研究了1',3'-二氢-1',3'-3'-三甲基-6-硝基螺[2H-1-苯并吡喃-2',2'-(2H)-吲哚]吸收紫外光子后形成的部花青（MC）异构体。在甲苯溶液中存在几种主要为TTC和TTT的部花青异构体（“T”和“C”表示次甲基桥中C-C键的反式和顺式构象）。使用100飞秒激光脉冲在MC可见吸收带（490、550和630纳米）进行激发，以研究MC的激发态动力学。发现皮秒时间尺度上的内转换是主要的弛豫途径。还观察到激发态异构化反应。在630纳米处激发（归因于TTC异构体激发）导致形成第三种异构体（CTC或CTT）。在490纳米处激发（归因于TTT异构体激发）导致更复杂的激发态弛豫，包括形成两种异构体：TTC（600纳米处吸收）和CTC或CTT（650纳米处吸收）。
