title: 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.
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.
authors.affiliation: Central Laser Facility, Science & Technology Facilities Council, Rutherford Appleton Laboratory, Harwell Science and Innovation Campus, Didcot, OX11 0QX, United Kingdom.
authors.forename: Ian P
authors.initials: IP
authors.lastname: Clark
authors.forename: Michael W
authors.initials: MW
authors.lastname: George
authors.forename: Gregory M
authors.initials: GM
authors.lastname: Greetham
authors.forename: Emma C
authors.initials: EC
authors.lastname: Harvey
authors.forename: Conor
authors.initials: C
authors.lastname: Long
authors.forename: Jennifer C
authors.initials: JC
authors.lastname: Manton
authors.forename: Mary T
authors.initials: MT
authors.lastname: Pryce
mesh_terms: D001565:Benzoates / Q000737:chemistry; D002248:Carbon Monoxide / Q000737:chemistry; D002857:Chromium / Q000737:chemistry; D006536:Heptanes / Q000737:chemistry*; D009281:Naphthalenes / Q000737:chemistry; D009942:Organometallic Compounds / Q000737:chemistry*; D010616:Phenanthrenes / Q000737:chemistry; D010777:Photochemistry; D012996:Solutions; D013055:Spectrophotometry, Infrared; D013997:Time Factors
chemical_list: D001565:Benzoates; D006536:Heptanes; D009281:Naphthalenes; D009942:Organometallic Compounds; D010616:Phenanthrenes; D012996:Solutions; D002857:Chromium; C031721:naphthalene; C031181:phenanthrene; C028618:n-heptane; D002248:Carbon Monoxide