title: Oxyallyl exposed: an open-shell singlet with picosecond lifetimes in solution but persistent in crystals of a cyclobutanedione precursor.
abstract: Photoinduced decarbonylation of 2,4-bis(spirocyclohexyl)-1,3-cyclobutanedione 1 in the crystalline solid state resulted in formation of a deep blue transient with λ(max) = 550 nm and a half-life of 42 min at 298 K, identified as kinetically stabilized oxyallyl. Support for an open-shell singlet species was obtained by spectroscopic analysis and (4/4) CASSCF calculations with the 6-31+G(d) basis set and multireference MP2 corrections. The electronic spectrum of the singlet biradical, confirmed by femtosecond pump-probe studies in solution, was matched by coupled cluster calculations with single and double corrections.
authors.affiliation: Department of Chemistry and Biochemistry, University of California, Los Angeles, California 90095-1559, USA.
authors.forename: Gregory
authors.initials: G
authors.lastname: Kuzmanich
authors.forename: Fabian
authors.initials: F
authors.lastname: Spänig
authors.forename: Chao-Kuan
authors.initials: CK
authors.lastname: Tsai
authors.forename: Joann M
authors.initials: JM
authors.lastname: Um
authors.forename: Ryan M
authors.initials: RM
authors.lastname: Hoekstra
authors.forename: K N
authors.initials: KN
authors.lastname: Houk
authors.forename: Dirk M
authors.initials: DM
authors.lastname: Guldi
authors.forename: Miguel A
authors.initials: MA
authors.lastname: Garcia-Garibay
mesh_terms: D002074:Butanones / Q000737:chemistry*; D018360:Crystallography, X-Ray; D007700:Kinetics; D008958:Models, Molecular; D015394:Molecular Structure; D055668:Photochemical Processes; D012996:Solutions; D013997:Time Factors
chemical_list: D002074:Butanones; D012996:Solutions