title: Temperature and pressure variations of d-d luminescence band maxima of bis(pyridylalkenolato)palladium(II) complexes with different ligand substituents: opposite-signed trends.
abstract: Luminescence spectra of two d(8)-configured bis(pyridylalkenolato)palladium(ii) complexes, [Pd{PyCHC(C3F7)O}2] and [Pd{PyCHC(CH3)O}2], are presented at variable temperature and pressure. Bands are assigned as d-d transitions. The heptafluoropropyl and methyl substituents on the ligands have different steric demands, influencing luminescence spectra. Broad bands with maxima at approximately 12 700 cm(-1) (790 nm) for ligands with heptafluoropropyl substituents and 12,100 cm(-1) (830 nm) for ligands with methyl substituents and widths of approximately 2100 cm(-1) for both complexes are observed at 80 K. Quenching of the luminescence is observed as temperature increases. The maxima of [Pd{PyCHC(C3F7)O}2] show a shift of -0.9 ± 0.1 cm(-1) K(-1) due to broadening of the spectra to lower energy. The luminescence maxima of [Pd{PyCHC(CH3)O}2] shift in the opposite direction by +7.2 ± 0.7 cm(-1) K(-1). Shifts with different signs are also obtained from variable-pressure luminescence spectra, with values of +13 ± 2 cm(-1) kbar(-1) and -15 ± 7 cm(-1) kbar(-1) for [Pd{PyCHC(C3F7)O}2] and [Pd{PyCHC(CH3)O}2], respectively. The pressure-induced decrease is unusual and likely caused by intermolecular interactions involving the palladium(ii) center and a vinylic proton of a neighboring complex.
authors.affiliation: Département de chimie, Université de Montréal, Montréal, Québec H3C 3J7, Canada. christian.reber@umontreal.ca.
authors.forename: Stéphanie
authors.initials: S
authors.lastname: Poirier
authors.affiliation: Institute of Inorganic Chemistry, University of Cologne, D-50939 Cologne, Germany.
authors.forename: Lisa
authors.initials: L
authors.lastname: Czympiel
authors.affiliation: Département de chimie, Université de Montréal, Montréal, Québec H3C 3J7, Canada. christian.reber@umontreal.ca.
authors.forename: Nicolas
authors.initials: N
authors.lastname: Bélanger-Desmarais
authors.affiliation: Institute of Inorganic Chemistry, University of Cologne, D-50939 Cologne, Germany.
authors.forename: Sanjay
authors.initials: S
authors.lastname: Mathur
authors.affiliation: Département de chimie, Université de Montréal, Montréal, Québec H3C 3J7, Canada. christian.reber@umontreal.ca.
authors.forename: Christian
authors.initials: C
authors.lastname: Reber