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Temperature and pressure variations of d–d luminescence band maxima of bis(pyridylalkenolato)palladium(II) complexes with different ligand substituents: opposite-signed trends

Stéphanie Poirier, Lisa Czympiel, Nicolas Bélanger-Desmarais, Sanjay Mathur and Christian Reber

Abstract

Luminescence spectra of two d8-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 12700 cm−1 (790 nm) for ligands with heptafluoropropyl substituents and 12100 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.

Dalton Trans., 2016, Advance Article

DOI: 10.1039/C5DT05068E

 

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