fac-Re(CO)3Cl Complexes of [2-(4-R-1H-1,2,3-Triazol-1-yl)methyl]pyridine Inverse 鈥淐lick鈥?Ligands: A Systematic Synthetic, Spectroscopic, and Computational Study

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• 作者：Christopher B. Anderson ; Anastasia B. S. Elliott ; C. John McAdam ; Keith C. Gordon ; James D. Crowley
• 刊名：Organometallics
• 出版年：2013
• 出版时间：February 11, 2013
• 年：2013
• 卷：32
• 期：3
• 页码：788-797
• 全文大小：502K
• 年卷期：v.32,no.3(February 11, 2013)
• ISSN：1520-6041

文摘

A series of electronically tuned fac-Re(CO)₃Cl inverse pyridyl-1,2,3-triazole complexes have been synthesized in good to excellent yields (72鈥?5%) by refluxing methanol solutions of [Re(CO)₅Cl] and the substituted [2-(4-R-1H-1,2,3-triazol-1-yl)methyl]pyridine ligands (py(CH₂)tri-R). The resulting rhenium(I) complexes were characterized by elemental analysis, HR-ESI-MS and IR and ¹H and ¹³C NMR spectroscopy. Additionally, the molecular structures of three of the complexes were confirmed using X-ray crystallography. The electronic properties of this series of fac-[(py(CH₂)tri-R)Re(CO)₃Cl] complexes were examined using UV鈥搗is, Raman, and emission spectroscopy and cyclic voltammetry techniques. The complexes exhibit intense absorptions in the UV region, which were modeled using time-dependent density functional theory (TD-DFT). The calculations suggest that the lower energy part of the absorption band is MLCT in nature and additional higher energy 蟺鈥撓€* transitions are present. The electronic spectra are nearly identical for all except where R = 4-nitrophenyl, suggesting that the 1,2,3-triazolyl unit acts as an electronic insulator. The TD-DFT calculations suggest that the lowest energy MLCT transition is polarized to the pyridine moiety for all complexes except the nitro-substituted one. With R = 4-nitrophenyl the MLCT is directed to an acceptor MO polarized to the triazole-R moiety. This finding is supported by resonance Raman studies that show enhancement of modes associated with the triazole-R group. The complexes are weakly emissive at room temperature with quantum yields <10^鈥? and correspondingly short excited-state lifetimes (蟿 < 20 ns). The electrochemistry of the complexes is defined by quasi-reversible Re oxidation and irreversible triazole-based ligand reduction processes. The nitro-substituted complexes show additional nitrobenzene-type reduction features. Consistent with the spectroscopic data, the positions of the oxidation and reduction processes are essentially unaffected by the electronic nature of the 2-(4-R-1H-1,2,3-triazol-1-yl)pyridine substituent.