Effect of N-methyl and ethyl on phosphorescence of carbazole in cocrystals assembled by C-I center dot center dot center dot pi halogen bond, pi-hole center dot center dot center dot pi bond and other interactions using 1,4-diiodotetrafluorobenzene as donor

摘要

Two phosphorescent cocrystals were prepared by 1,4-diiodotetrafluorobenzene (1,4-DITFB) and N-methylcarbazole (cocrystal 1) and N-ethylcarbazole (cocrystal 2) based on C-I center dot center dot center dot pi halogen bond, pi-hole (pi h)center dot center dot center dot pi bond and C-H center dot center dot center dot pi, C-H center dot center dot center dot F hydrogen bond as well as F center dot center dot center dot F contacts, in which 1,4-DITFB molecule acts simultaneously as the cement to link luminescence molecules and the heavy atom per-turber to enhance phosphorescence of emitters by spin-orbital coupling. The cocrystals were also well characterized by powder XRD, FT-IR, Raman, DSC and DTA analysis and also estimated the bonding energies by calculation. Different steric effects of N-substituted groups on the carbazole backbone leads to the different C-I center dot center dot center dot pi bonding stoichiometry and pi-hole center dot center dot center dot pi bonding modes and then lead to the phosphorescence spectra red- or blue-shift compared with carbazole-1,4-diiodotetrafluorobenzene cocrystal. (C) 2014 Elsevier B.V. All rights reserved.