A spectroscopic and computational study on the effects of methyl and phenyl substituted phenanthroline ligands on the electronic structure of Re(i) tricarbonyl complexes containing 2,6-dimethylphenylisocyanide
作者:John M. Villegas、Stanislav R. Stoyanov、Wei Huang、D. Paul Rillema
DOI:10.1039/b415079a
日期:——
[Re(CO)3(CNx)(L)]+, where CNx = 2,6-dimethylphenylisocyanide, forms complexes with L = 1,10-phenanthroline (1), 4-methyl-1,10-phenanthroline (2), 4,7-dimethyl-1,10-phenanthroline (3), 3,4,7,8-tetramethyl-1,10-phenanthroline (4), 2,9-dimethyl-1,10-phenanthroline (5) and 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (6). The metal–ligand-to-ligand charge transfer transition (MLLCT) absorption bands follow the series: 3
(27 800 cm−1) > 1, 2, 4 and 5
(27 500 cm−1) > 6
(26 600 cm−1). Density functional theory (DFT) geometry optimizations reveal elongated Re–N (L) distances of 2.28 and 2.27 Å for 5 and 6, respectively, compared to 2.23 Å for 1–4. The reversible reduction potentials (E1/2(red)) of 1–4 are linearly dependent on the B3LYP calculated LUMO energies. Time-dependent (TD) DFT and conductor-like polarizable continuum model (CPCM) calculated singlet excited states deviate by 700 cm−1 or less from the experimental absorption maxima and aid in the spectral assignments. The 3MLLCT emitting state energies are within 900 cm−1 of the experimental 77 K emission energies for 1–6. The 77 K emission energies, E1/2(red), and the room temperature emission quantum yields (ϕLUMOem) decrease in the order 1 > 2 > 3 > 4 whereas ELUMO and the room temperature emission energies follow the opposite trend. The emission lifetimes (τem) decrease in the order 3 > 4 > 2 > 1 > 5 with 3 having the highest emission lifetime values of 26.9 µs at room temperature and 384 µs at 77 K and complex 5 having the lowest emission lifetimes of 4.6 µs at room temperature and 61 µs and 77 K.
[Re(CO)3(CNx)(L)]+,其中 CNx = 2,6-二甲基苯基异氰化物,与 L = 1,10-菲咯啉 (1)、4-甲基-1,10-菲咯啉 (2)、4,7-二甲基-1,10-菲咯啉 (3)、3,4,7,8-四甲基-1,10-菲咯啉 (4)、2,9-二甲基-1,10-菲咯啉 (5) 和 2,9-二甲基-4,7-二苯基-1,10-菲咯啉 (6) 形成配合物。金属-配体-配体电荷转移跃迁 (MLLCT) 吸收带遵循以下系列:3 (27,800 cm−1) > 1、2、4 和 5 (27,500 cm−1) > 6 (26,600 cm−1)。密度泛函理论 (DFT) 几何优化揭示了 5 和 6 的 Re–N (L) 距离分别为 2.28 和 2.27 Å,而 1–4 的 Re–N (L) 距离为 2.23 Å。可逆还原电位 (E1/2(red)) 1–4 与 B3LYP 计算的 LUMO 能量线性相关。含时 (TD) DFT 和类导体可极化连续模型 (CPCM) 计算的单重激发态与实验吸收最大值的偏差不超过 700 cm−1,有助于光谱归属。3MLLCT 发射态能量在 1–6 的 77 K 发射能量范围内,误差在 900 cm−1 以内。77 K 发射能量、E1/2(red) 以及室温发射量子产率 (ϕLUMOem) 按以下顺序递减:1 > 2 > 3 > 4,而 LUMO 能量和室温发射能量则相反。发射寿命 (τem) 按以下顺序递减:3 > 4 > 2 > 1 > 5,其中 3 在室温下的发射寿命值最高,为 26.9 μs,在 77 K 下为 384 μs,而配合物 5 的发射寿命最低,室温下为 4.6 μs,77 K 下为 61 μs。