title: N-heterocyclic carbene Pt(II) complexes from caffeine: synthesis, structures and photoluminescent properties.
abstract: The caffeine-derived N-heterocyclic carbene (NHC) complex [Pt(II)(C^N)(NHC)Cl] (C^N = 2-phenylpyridine), 4 has the opposite stereochemistry and a shorter Pt-C(carbene) bond compared to that of an analogous benzimidazole-derived N,N-heterocyclic carbene (NNHC) Pt complex 2. These suggest a lower trans influence of pyridyl N compared to cyclometallated carbon and an increased Pt-NHC π-backbonding because of decreased π-donation resulting from conjugation to the electron deficient pyrimidine of caffeine. Complex 4 has a lower emission quantum yield (Φ) and is blue-shifted into the green region of the visible spectrum relative to non-carbene Pt(II) cyclometalated complex 5.
authors.affiliation: Department of Chemistry, National University of Singapore, 3 Science Drive, Singapore 117543.
authors.forename: Jian Jin
authors.initials: JJ
authors.lastname: Hu
authors.forename: Shi-Qiang
authors.initials: SQ
authors.lastname: Bai
authors.forename: Hsiu Hsuan
authors.initials: HH
authors.lastname: Yeh
authors.forename: David J
authors.initials: DJ
authors.lastname: Young
authors.forename: Yun
authors.initials: Y
authors.lastname: Chi
authors.forename: T S Andy
authors.initials: TS
authors.lastname: Hor
mesh_terms: D002110:Caffeine / Q000737:chemistry*; D056831:Coordination Complexes / Q000138:chemical synthesis* / Q000737:chemistry; D018360:Crystallography, X-Ray; D006571:Heterocyclic Compounds / Q000737:chemistry; D008697:Methane / Q000031:analogs & derivatives* / Q000737:chemistry; D008968:Molecular Conformation; D010984:Platinum / Q000737:chemistry*; D011789:Quantum Theory; D013056:Spectrophotometry, Ultraviolet
chemical_list: D056831:Coordination Complexes; D006571:Heterocyclic Compounds; C030011:carbene; D002110:Caffeine; D010984:Platinum; D008697:Methane