Adams Christopher J, Fey Natalie, Harrison Zoë A, Sazanovich Igor V, Towrie Michael, Weinstein Julia A
School of Chemistry, University of Bristol, Bristol BS8 1TS, UK.
Inorg Chem. 2008 Sep 15;47(18):8242-57. doi: 10.1021/ic800850h. Epub 2008 Aug 9.
The compounds [Pt(MesBIAN)(C[triple bond]CR)2] (R = C6H4-CN-p, 1; SiMe3, 2; C6H4-CF3-p, 3; C6H5, 4; C6H4-CH3-p 5) {MesBIAN = bis(mesitylimino)acenaphthene} have been synthesized; the X-ray crystal structure determinations of 4 and 5 and the starting material [Pt(MesBIAN)Cl2] are reported. Chemical oxidation of 4 with diiodine leads to generation of an intermediate platinum(IV) bis(acetylide) diiodide complex, which then couples and reductively eliminates the acetylide ligands as a diyne, leading to the generation of [Pt(MesBIAN)I2] 6. Compound 2 readily forms an adduct 2a with copper(I) chloride, in which the copper atom is bonded to the two acetylide triple bonds. 1-5 each undergo an irreversible oxidation, and a reversible one-electron reduction to generate a stable anion. ESR studies of 1(-)-5(-) show that the unpaired electron is localized mainly on the pi* orbital of the coordinated MesBIAN ligand, with about 10% platinum contribution to the singly occupied molecular orbital (SOMO). The compounds show a strong absorption at around 500 nm in the UV/visible spectrum, which is assigned to a "mixed metal-ligand to ligand charge transfer" (MMLL'CT) transition; this assignment is supported by time-dependent density-functional theory (TD-DFT) calculations on 5. 1-5 emit in the near-infrared region from a (3)MMLL'CT excited state, with lifetimes ranging from 8 to 36 ns. Picosecond and nanosecond time-resolved infrared (TRIR) spectroscopy has been used to probe directly the nature and dynamics of the excited state of 5. The TRIR data show a decrease of the energy of the C[triple bond]C vibration upon excitation, by about 90 cm(-1) in comparison to the ground state, and formation of a new, very intense, and very broad band at 1820 cm(-1). We propose that the excited-state structure contains some contribution from a pseudo-cumulenic form of the platinum-acetylide moiety, which is supported by TD-DFT calculations. Picosecond TRIR allowed determination of the rate of vibrational relaxation (14 ps) of the vibrationally "hot" electronic excited state of 5 formed upon initial laser excitation.
已合成化合物[Pt(MesBIAN)(C≡CR)₂]（R = C₆H₄-CN-p，1；SiMe₃，2；C₆H₄-CF₃-p，3；C₆H₅，4；C₆H₄-CH₃-p，5）{MesBIAN = 双（均三甲苯基亚氨基）苊烯}；报道了4和5以及起始原料[Pt(MesBIAN)Cl₂]的X射线晶体结构测定结果。用碘对4进行化学氧化会生成一种中间体铂(IV)双（乙炔基）二碘配合物，该配合物随后偶联并还原消除乙炔基配体形成二炔，从而生成[Pt(MesBIAN)I₂] 6。化合物2很容易与氯化亚铜形成加合物2a，其中铜原子与两个乙炔基三键相连。1 - 5均经历不可逆氧化以及可逆的单电子还原以生成稳定阴离子。对1⁻ - 5⁻的电子顺磁共振（ESR）研究表明，未成对电子主要定域在配位的MesBIAN配体的π*轨道上，铂对单占据分子轨道（SOMO）的贡献约为10%。这些化合物在紫外/可见光谱中约500 nm处有强吸收，这归因于“混合金属 - 配体到配体电荷转移”（MMLL'CT）跃迁；对5进行的含时密度泛函理论（TD - DFT）计算支持了这一归属。1 - 5从（³）MMLL'CT激发态在近红外区域发射，寿命范围为8至36 ns。皮秒和纳秒时间分辨红外（TRIR）光谱已用于直接探测5的激发态的性质和动力学。TRIR数据表明，激发后C≡C振动的能量降低，与基态相比降低约90 cm⁻¹，并在1820 cm⁻¹处形成一个新的、非常强且非常宽的谱带。我们提出激发态结构包含铂 - 乙炔基部分的拟累积烯形式的一些贡献，TD - DFT计算支持了这一点。皮秒TRIR能够测定初始激光激发后形成的5振动ally“热”电子激发态的振动弛豫速率（14 ps）。
