Excited-State Characteristics of Tetracyanidonitridorhenium(V) and -technetium(V) Complexes with N-Heteroaromatic Ligands

详细信息    查看全文

• 作者：Hayato Ikeda ; Akitaka Ito ; Eri Sakuda ; Noboru Kitamura ; Tsutomu Takayama ; Tsutomu Sekine ; Atsushi Shinohara ; Takashi Yoshimura
• 刊名：Inorganic Chemistry
• 出版年：2013
• 出版时间：June 3, 2013
• 年：2013
• 卷：52
• 期：11
• 页码：6319-6327
• 全文大小：397K
• 年卷期：v.52,no.11(June 3, 2013)
• ISSN：1520-510X

文摘

Six-coordinate tetracyanidonitridorhenium(V) and -technetium(V) with axial N-heteroaromatic ligands, (PPh₄)₂[MN(CN)₄L] [M = Re, L = 4-(dimethylamino)pyridine (dmap), 3,5-lutidine (lut), 4-picoline (pic), 4-phenylpyridine (ppy), pyridine (py), 3-benzoylpyridine (3bzpy), 4,4鈥?bipyridine (bpy), pyrazine (pz), 4-cyanopyridine (cpy), or 4-benzoylpyridine (4bzpy); M = Tc, L = dmap, lut, pic, py, pz, or cpy] were synthesized and characterized. The crystal structures of 11 complexes were determined by single-crystal X-ray analysis. All of the complexes showed photoluminescence in the crystalline phase at room temperature. The emission maximum wavelengths (位_em) of the rhenium complexes with dmap, lut, pic, ppy, or py were similar to one another with a quite high emission quantum yield (桅_em): 位_em = 539鈥?45 nm, 桅_em = 0.39鈥?.93, and emission lifetime (蟿_em) = 10鈥?5 渭s at 296 K. The emission spectra at 77 K exhibited vibronic progressions, and the emissive excited state is characterized as ³[(d_xy)¹(d_蟺*)¹] (d_蟺* = d_xz, d_yz). On the other hand, the emission maximum wavelength of the rhenium complex with 3bzpy, bpy, pz, cpy, or 4bzpy was significantly dependent on the nature of the axial ligand in the crystalline phase: 位_em = 564鈥?69 nm, 桅_em 鈮?0.01鈥?.36, and 蟿_em = 0.03鈥?3.3 渭s at 296 K. The emission spectra at 77 K in the crystalline phase did not show vibronic progressions. The emissive excited state of the rhenium complex with bpy, pz, cpy, or 4bzpy is assignable to originate from the metal-to-N-heteroaromatic ligand charge-transfer (MLCT)-type emission with a spin-triplet type. The change in the excited-state characteristics of rhenium complexes by the N-heteroaromatic ligand is a result of stabilization of the 蟺* orbital of the N- heteroaromatic ligand to a lower energy level than the d_蟺* orbitals. The emission spectral shapes of technetium complexes were almost independent of the nature of the N-heteroaromatic ligand with 位_em = 574鈥?81 nm at room temperature. The different emission characteristics between the pz and cpy coordinate rhenium complexes and the technetium analogues would be due to stabilization of technetium-centered orbitals compared with the rhenium ones in energy.