Photochemistry of (η(6)-arene)Cr(CO)3 (arene = methylbenzoate, naphthalene, or phenanthrene) in n-heptane solution: population of two excited states following 400 nm excitation as detected by picosecond time-resolved infrared spectroscopy

J Phys Chem A. 2011 Apr 14;115(14):2985-93. doi: 10.1021/jp112168u. Epub 2011 Mar 17.

Abstract

The photochemistry of (η(6)-methylbenzoate)Cr(CO)(3), (η(6)-naphthalene)Cr(CO)(3), and (η(6)-phenanthrene)Cr(CO)(3) in n-heptane solution was investigated by picosecond time-resolved infrared spectroscopy (TRIR). The observation of two transient IR features in the organic carbonyl region at 1681 and 1724 cm(-1) following 400 nm excitation of (η(6)-methylbenzoate)Cr(CO)(3) confirms formation of two excited states which are classified as metal-to-arene charge transfer (MACT) and metal-to-CO charge transfer (MCCT), respectively. Time-dependent density functional theory calculations have been used to support these assignments. Population of the MCCT excited state results in a slow (150 ps) expulsion of one CO ligand. Excitation of (η(6)-naphthalene)Cr(CO)(3) or (η(6)-phenanthrene)Cr(CO)(3) at either 400 or 345 nm produced two excited states: the MCCT state results in CO loss, while the MACT excited state results in a change to the coordination mode of the polyaromatic ligands before relaxing to the parent complex. A comparison of the infrared absorptions observed following the population of the MACT excited state with those calculated for nonplanar polyaromatic intermediates provides a model for the reduced hapticity species.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Benzoates / chemistry
  • Carbon Monoxide / chemistry
  • Chromium / chemistry
  • Heptanes / chemistry*
  • Naphthalenes / chemistry
  • Organometallic Compounds / chemistry*
  • Phenanthrenes / chemistry
  • Photochemistry
  • Solutions
  • Spectrophotometry, Infrared
  • Time Factors

Substances

  • Benzoates
  • Heptanes
  • Naphthalenes
  • Organometallic Compounds
  • Phenanthrenes
  • Solutions
  • Chromium
  • naphthalene
  • phenanthrene
  • n-heptane
  • Carbon Monoxide