首页> 外文OA文献 >Excited-State Dynamics offac-Re^I(L)(CO)_3(phen)^+ and fac-Re^I(L)(CO)_3(5-NO_(2-)phen)^+(L = Imidazole, 4-Ethylpyridine; Phen = 1,10-Phenanthroline) Complexes
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Excited-State Dynamics offac-Re^I(L)(CO)_3(phen)^+ and fac-Re^I(L)(CO)_3(5-NO_(2-)phen)^+(L = Imidazole, 4-Ethylpyridine; Phen = 1,10-Phenanthroline) Complexes

机译:激发态动力学offac- Re ^ I(L)(CO)_3(phen) ^ +和fac- Re ^ I(L)(CO)_3(5-NO_(2-)phen) ^ + (L =咪唑,4-乙吡啶;苯酚= 1,10-菲咯啉)配合物

摘要

The nature and dynamics of the lowest excited states of fac-[Re^I(L)(CO)_3(phen)]^+ and fac-[Re^I(L)(CO)_3(5-NO_2-phen)]^+ [L = Cl-, 4-ethyl-pyridine (4-Etpy), imidazole (imH); phen = 1,10-phenanthroline] have been investigated by picosecond visible and IR transient absorption spectroscopy in aqueous (L = imH), acetonitrile (L = 4-Etpy, imH), and MeOH (L = imH) solutions. The phen complexes have long-lived Re^I → phen ^3MLCT excited states, characterized by CO stretching frequencies that are upshifted relative to their ground-state values and by widely split IR bands due to the out-of-phase A‘(2) and A‘ ‘ ν(CO) vibrations. The lowest excited states of the 5-NO_(2-)phen complexes also have ^3MLCT character; the larger upward ν(CO) shifts accord with much more extensive charge transfer from the Re^I(CO)_3 unit to 5-NO_(2-)phen in these states. Transient visible absorption spectra indicate that the excited electron is delocalized over the 5-NO_(2-)phen ligand, which acquires radical anionic character. Similarly, involvement of the -NO_2 group in the Franck−Condon MLCT transition is manifested by the presence of an enhanced ν(NO_2) band in the preresonance Raman spectrum of [Re^I(4-Etpy)(CO)_3(5-NO_(2-)phen)]^+. The Re^I → 5-NO_(2-)phen ^3MLCT excited states are very short-lived:  7.6, 170, and 43 ps for L = Cl-, 4-Etpy, and imH, respectively, in CH_3CN solutions. The ^3MLCT excited state of [Re^I(imH)(CO)_3(5-NO_(2-)phen)]^+ is even shorter-lived in MeOH (15 ps) and H_2O (1.3 ps). In addition to ^3MLCT, excitation of [Re^I(imH)(CO)_3(5-NO_(2-)phen)]^+ populates a ^3LLCT (imH → 5-NO_(2-)phen) excited state. Most of the ^3LLCT population decays to the ground state (time constants of 19 (H_2O), 50 (MeOH), and 72 ps (CH_3CN)); in a small fraction, however, deprotonation of the imH^(•+) ligand occurs, producing a long-lived species, [Re^I(im^•)(CO)_3(5-NO_(2-)phen)^(•-)]^+.
机译:fac- [Re ^ I(L)(CO)_3(phen)] ^ +和fac- [Re ^ I(L)(CO)_3(5-NO_2-phen)的最低激发态的性质和动力学] ^ + [L = Cl-,4-乙基吡啶(4-Etpy),咪唑(imH); phen = 1,10-菲咯啉]已通过皮秒可见光和IR瞬态吸收光谱法在水溶液(L = imH),乙腈(L = 4-Etpy,imH)和MeOH(L = imH)溶液中进行了研究。 phen络合物具有长寿命的Re ^ I→phen ^ 3MLCT激发态,其特征在于CO拉伸频率相对于其基态值上移,并且由于A'(200)相异而具有广泛的IR波段)和A''ν(CO)振动。 5-NO_(2-)phen配合物的最低激发态也具有^ 3MLCT特性;在这些状态下,较大的向上ν(CO)位移与从Re ^ I(CO)_3单元到5-NO_(2-)phen的更广泛的电荷转移相一致。瞬态可见吸收光谱表明,激发的电子在5-NO_(2-)phen配体上离域化,该配体具有自由基阴离子特性。类似地,-NO_2基团参与了Franck-Condon MLCT转变,其表现为[Re ^ I(4-Etpy)(CO)_3(5-)的先共振拉曼光谱中存在增强的ν(NO_2)带。 NO_(2-)phen)] ^ +。 Re ^ I→5-NO_(2-)phen ^ 3MLCT的激发态寿命很短:在CH_3CN溶液中,对于L = Cl-,4-Etpy和imH,分别为7.6、170和43 ps。 [Re ^ I(imH)(CO)_3(5-NO_(2-)phen)] ^ +的^ 3MLCT激发态在MeOH(15 ps)和H_2O(1.3 ps)中的寿命更短。除了^ 3MLCT,[Re ^ I(imH)(CO)_3(5-NO_(2-)phen)] ^ +的激发还构成了^ 3LLCT(imH→5-NO_(2-)phen)激发态。大部分^ 3LLCT种群衰减到基态(时间常数为19(H_2O),50(MeOH)和72 ps(CH_3CN));然而,在很小的一部分中,imH ^(•+)配体就会发生去质子化反应,从而产生长寿命的物质[Re ^ I(im ^•)(CO)_3(5-NO_(2-)phen)^ (•-)] ^ +。

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