Electronic and Molecular Structures of trans-Dioxotechnetium(V) Polypyridyl Complexes in the Solid State

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• 作者：Sayandev Chatterjee ; Andrew S. Del Negro ; Zheming Wang ; Matthew K. Edwards ; Frances N. Skomurski ; Sean E. Hightower ; Jeanette A. Krause ; Brendan Twamley ; B. Patrick Sullivan ; Christian Reber ; William R. Heineman ; Carl J. Seliskar ; Samuel A. Bryan
• 刊名：Inorganic Chemistry
• 出版年：2011
• 出版时间：June 20, 2011
• 年：2011
• 卷：50
• 期：12
• 页码：5815-5823
• 全文大小：953K
• 年卷期：v.50,no.12(June 20, 2011)
• ISSN：1520-510X

文摘

The structures of novel Tc(V) complexes trans-[TcO<sub>2sub>(py)<sub>4sub>]Cl路2H<sub>2sub>O (1a), trans-[TcO<sub>2sub>(pic)<sub>4sub>]Cl路2H<sub>2sub>O (2a), and trans-[TcO<sub>2sub>(pic)<sub>4sub>]BPh<sub>4sub> (2b) were determined by X-ray crystallography, and their spectroscopic characteristics were investigated by emission spectroscopy and atomic scale calculations. The cations adopt a tetragonally distorted octahedral geometry, with a trans orientation of the apical oxo groups. trans-[TcO<sub>2sub>(pic)<sub>4sub>]BPh<sub>4sub> has an inversion center located on technetium; however, for trans-[TcO<sub>2sub>(py)<sub>4sub>]Cl路2H<sub>2sub>O and trans-[TcO<sub>2sub>(pic)<sub>4sub>]Cl路2H<sub>2sub>O, a strong H bond formed by only one of the oxo substituents introduces an asymmetry in the structure, resulting in inequivalent trans Tc鈥揘 and Tc鈺怬 distances. Upon 415 nm excitation at room temperature, the complexes exhibited broad, structureless luminescences with emission maxima at approximately 710 nm (1a) and 750 nm (2a, 2b). Like the Re(V) analogs, the Tc(V) complexes luminesce from a <sup>3sup>E<sub>gsub> excited state. Upon cooling the samples from 278 to 8 K, distinct vibronic features appear in the spectra of the complexes along with increases in emission intensities. The low temperature emission spectra display the characteristic progressions of the symmetric O鈺怲c鈺怬 and the Tc鈥揕 stretching modes. Lowest-energy, triplet excited-state distortions calculated using a time-dependent theoretical approach are in good agreement with the experimental spectra. The discovery of luminescence from the trans-dioxotechnetium(V) complexes provides the first opportunity to directly compare fundamental luminescence properties of second- and third-row d<sup>2sup> metal-oxo congeners.