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Title: Ground-state and excited-state structures of tungsten-benzylidyne complexes

Abstract

The molecular structure of the tungsten-benzylidyne complex trans-W({triple_bond}CPh)(dppe){sub 2}Cl (1; dppe = 1,2-bis(diphenylphosphino)ethane) in the singlet (d{sub xy}){sup 2} ground state and luminescent triplet (d{sub xy}){sup 1}({pi}*(WCPh)){sup 1} excited state (1*) has been studied using X-ray transient absorption spectroscopy, X-ray crystallography, and density functional theory (DFT) calculations. Molecular-orbital considerations suggest that the W-C and W-P bond lengths should increase in the excited state because of the reduction of the formal W-C bond order and decrease in W {yields} P {pi}-backbonding, respectively, between 1 and 1*. This latter conclusion is supported by comparisons among the W-P bond lengths obtained from the X-ray crystal structures of 1, (d{sub xy}){sup 1}-configured 1{sup +}, and (d{sub xy}){sup 2} [W(CPh)(dppe){sub 2}(NCMe)]{sup +} (2{sup +}). X-ray transient absorption spectroscopic measurements of the excited-state structure of 1* reveal that the W-C bond length is the same (within experimental error) as that determined by X-ray crystallography for the ground state 1, while the average W-P/W-Cl distance increases by 0.04 {angstrom} in the excited state. The small excited-state elongation of the W-C bond relative to the M-E distortions found for M({triple_bond}E)L{sub n} (E = O, N) compounds with analogous (d{sub xy}){sup 1}({pi}*(ME)){sup 1} excited states is due to themore » {pi} conjugation within the WCPh unit, which lessens the local W-C {pi}-antibonding character of the {pi}*(WCPh) lowest unoccupied molecular orbital (LUMO). These conclusions are supported by DFT calculations on 1 and 1*. The similar core bond distances of 1, 1{sup +}, and 1* indicates that the inner-sphere reorganization energy associated with ground- and excited-state electron-transfer reactions is small.« less

Authors:
; ; ; ; ; ; ;  [1]
  1. Chemical Sciences and Engineering Division
Publication Date:
Research Org.:
Argonne National Lab. (ANL), Argonne, IL (United States)
Sponsoring Org.:
SC BASIC ENERGY SCIENCES
OSTI Identifier:
1051239
Report Number(s):
ANL/CSE/JA-74237
Journal ID: ISSN 0020-1669; INOCAJ; TRN: US201218%%1338
DOE Contract Number:  
DE-AC02-06CH11357
Resource Type:
Journal Article
Journal Name:
Inorganic Chemistry
Additional Journal Information:
Journal Volume: 51; Journal Issue: 10; Journal ID: ISSN 0020-1669
Country of Publication:
United States
Language:
ENGLISH
Subject:
36 MATERIALS SCIENCE; ABSORPTION; ABSORPTION SPECTROSCOPY; BOND LENGTHS; CRYSTAL STRUCTURE; CRYSTALLOGRAPHY; ELECTRON TRANSFER; ELONGATION; EXCITED STATES; FUNCTIONALS; GROUND STATES; MOLECULAR STRUCTURE; TRANSIENTS; TRIPLETS

Citation Formats

Lovaasen, B M, Lockard, J V, Cohen, B W, Yang, S, Zhang, X, Simpson, C K, Chen, L X, Hopkins, M D, XSD), and The Univ. of Chicago). Ground-state and excited-state structures of tungsten-benzylidyne complexes. United States: N. p., 2012. Web. doi:10.1021/ic202622s.
Lovaasen, B M, Lockard, J V, Cohen, B W, Yang, S, Zhang, X, Simpson, C K, Chen, L X, Hopkins, M D, XSD), & The Univ. of Chicago). Ground-state and excited-state structures of tungsten-benzylidyne complexes. United States. doi:10.1021/ic202622s.
Lovaasen, B M, Lockard, J V, Cohen, B W, Yang, S, Zhang, X, Simpson, C K, Chen, L X, Hopkins, M D, XSD), and The Univ. of Chicago). Sun . "Ground-state and excited-state structures of tungsten-benzylidyne complexes". United States. doi:10.1021/ic202622s.
@article{osti_1051239,
title = {Ground-state and excited-state structures of tungsten-benzylidyne complexes},
author = {Lovaasen, B M and Lockard, J V and Cohen, B W and Yang, S and Zhang, X and Simpson, C K and Chen, L X and Hopkins, M D and XSD) and The Univ. of Chicago)},
abstractNote = {The molecular structure of the tungsten-benzylidyne complex trans-W({triple_bond}CPh)(dppe){sub 2}Cl (1; dppe = 1,2-bis(diphenylphosphino)ethane) in the singlet (d{sub xy}){sup 2} ground state and luminescent triplet (d{sub xy}){sup 1}({pi}*(WCPh)){sup 1} excited state (1*) has been studied using X-ray transient absorption spectroscopy, X-ray crystallography, and density functional theory (DFT) calculations. Molecular-orbital considerations suggest that the W-C and W-P bond lengths should increase in the excited state because of the reduction of the formal W-C bond order and decrease in W {yields} P {pi}-backbonding, respectively, between 1 and 1*. This latter conclusion is supported by comparisons among the W-P bond lengths obtained from the X-ray crystal structures of 1, (d{sub xy}){sup 1}-configured 1{sup +}, and (d{sub xy}){sup 2} [W(CPh)(dppe){sub 2}(NCMe)]{sup +} (2{sup +}). X-ray transient absorption spectroscopic measurements of the excited-state structure of 1* reveal that the W-C bond length is the same (within experimental error) as that determined by X-ray crystallography for the ground state 1, while the average W-P/W-Cl distance increases by 0.04 {angstrom} in the excited state. The small excited-state elongation of the W-C bond relative to the M-E distortions found for M({triple_bond}E)L{sub n} (E = O, N) compounds with analogous (d{sub xy}){sup 1}({pi}*(ME)){sup 1} excited states is due to the {pi} conjugation within the WCPh unit, which lessens the local W-C {pi}-antibonding character of the {pi}*(WCPh) lowest unoccupied molecular orbital (LUMO). These conclusions are supported by DFT calculations on 1 and 1*. The similar core bond distances of 1, 1{sup +}, and 1* indicates that the inner-sphere reorganization energy associated with ground- and excited-state electron-transfer reactions is small.},
doi = {10.1021/ic202622s},
journal = {Inorganic Chemistry},
issn = {0020-1669},
number = 10,
volume = 51,
place = {United States},
year = {2012},
month = {1}
}