Kasha or state selective behavior in the photochemistry of ortho-nitrobenzaldehyde?
Kasha or state selective behavior in the photochemistry of ortho-nitrobenzaldehyde?
复制标题
DOI：
10.1039/c2pp25057h
复制
发表时间：
2012-07
影响因子：
3.1
通讯作者：
T. Schmierer;G. Ryseck;Torben Villnow;N. Regner;P. Gilch
中科院分区：
文献类型：
--
作者：
T. Schmierer;G. Ryseck;Torben Villnow;N. Regner;P. Gilch
用飞秒紫外可见光谱和红外光谱研究了邻硝基苯甲醛在四氢呋喃溶液中的光化学行为。比较了~400 nm和~260 nm激发下的光谱和时间特征。当激发波长为2 60 nm时，最低激发态为nπ*特征，激发态为ππ*特征。在皮秒时间尺度上，分子经历氢转移，生成酮中间体，内转化恢复起始物质，以及系间交叉。这些过程的时间常数和产额几乎不受激发波长的影响。对于4 0 0 nm激发，没有在2 6 0 nm实验中看到的~10 0ps衰变分量，这表明该分量是由ππ*→nπ*内转换引起的。与其形成相反，烯酮中间体的衰变受激发波长的影响。这可以归因于不同数量的振动激发。
The photochemistry of ortho -nitrobenzaldehyde dissolved in tetrahydrofuran was studied by means of femtosecond UV/Vis and IR spectroscopy. Comparison was made of the spectral and temporal signatures for ~400 nm and ~260 nm excitation. The 400 nm excitation promotes NBA to its lowest excited singlet state of nπ* character whereas for 260 nm an upper excited state of ππ* character is addressed. On the picosecond time scale, the molecule undergoes hydrogen transfer, yielding a ketene intermediate, internal conversion recovering the starting material, and intersystem crossing. Time constants and yields of these processes are virtually not affected by the excitation wavelength. For 400 nm excitation a ~100 fs decay component seen in the 260 nm experiment is absent, indicating that this component is due to a ππ* → nπ* internal conversion. In contrast to its formation, the decay of the ketene intermediate is influenced by the excitation wavelength. This can be attributed to different amounts of vibrational excitation.