Re(I) Complexes of Substituted dppz: A Computational and Spectroscopic Study
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- 作者：Holly van der Salm ; Michael G. Fraser ; Raphael Horvath ; Scott A. Cameron ; Jonathan E. Barnsley ; Xue-Zhong Sun ; Michael W. George ; Keith C. Gordon
- 刊名：Inorganic Chemistry
- 出版年：2014
- 出版时间：March 17, 2014
- 年：2014
- 卷：53
- 期：6
- 页码：3126-3140
- 全文大小：735K
- 年卷期：v.53,no.6(March 17, 2014)
- ISSN：1520-510X
文摘
A series of dipyrido[3,2-a:2鈥?3鈥?c]phenazine (dppz)-based ligands with electron-withdrawing substituents and their [Re(CO)3(L)Cl] and [Re(CO)3(L)(py)]PF6 complexes have been studied using Raman, resonance Raman, and transient resonance Raman (TR2) and time-resolved infrared (TRIR) spectroscopic techinques in conjunction with computational chemistry as well as electrochemical studies, emission, and absorption of ground and excited states. DFT (B3LYP) frequency calculations show good agreement with nonresonant Raman spectra, which allowed these to be used to identify phenanthroline, phenazine, and delocalized modes. These band assignments were used to establish the nature of chromophores active in resonance Raman spectra, probed with wavelengths between 350.7 and 457.9 nm. X-ray crystallography of [Re(CO)3(dppzBr2)Cl] and [Re(CO)3(dppzBr)(py)]PF6 showed these crystallize in space groups triclinic P1 and monoclinic P21/n, respectively. Electrochemical studies showed that substituents have a strong effect on the phenazine MO, changing the reduction potential by 200 mV. Transient absorption studies showed that generally the [Re(CO)3(L)(py)]PF6 complexes had longer lifetimes than the corresponding [Re(CO)3(L)Cl] complexes; the probed state is likely to be 3蟺 鈫?蟺* (phz) in nature. TR2 spectra of the ligands provided a marker for the triplet 蟺 鈫?蟺* state, and the TR2 spectra of the complexes suggest an intraligand (IL) 蟺,蟺* state for [Re(CO)3(L)(py)]+ complexes, and a potentially mixed IL/MLCT state for [Re(CO)3(L)Cl] complexes. TRIR spectroscopy is more definitive with THEXI state assignments, and analysis of the metal鈥揷arbonyl region (1800鈥?100 cm鈥?) on the picosecond and nanosecond time scales indicates the formation of MLCT(phen/phz) states for all [Re(CO)3(L)Cl] complexes, and IL 蟺 鈫?蟺* (phen) states for all [Re(CO)3(L)(py)]+ complexes, with all but [Re(CO)3(dppzBr(CF3))(py)]+ showing some contribution from an MLCT(phen) state also.