title: Phenothiazine decorated carbazoles: effect of substitution pattern on the optical and electroluminescent characteristics.
abstract: A series of thienylphenothiazine decorated carbazoles were synthesized and characterized by optical, electrochemical, thermal, and theoretical investigations. Absorption spectra of the compounds are influenced by the substitution pattern and chromophore number density. Compounds containing 2,7-substitution exhibited red-shifted absorption, while the chromophore loading on the other positions led to the increment in molar extinction coefficients due to the increase in the chromophore density. Multiple substitutions resulted in twisting of chromophores and affected the conjugative delocalization of the π-electrons, which produced shorter wavelength absorption for the 2,3,6,7-tetrasubstituted derivative. Interestingly, the compounds exhibited excited-state solvatochromism attributable to the structural reorganization-induced electronic perturbations. The solvatochromic data are supportive of a general solvent effect, which is further confirmed by Lippert-Mataga correlation. End-capping with butterfly shaped phenothiazine restrained the formation of molecular aggregates in the solid state. All of the compounds displayed exceptional thermal stability attributable to the rigid carbazole building block. Solution processed OLED fabricated using the new materials as emitting dopants in 4,4'-bis(9H-carbazol-9-yl)biphenyl host exhibited bluish green electroluminescence.
authors.affiliation: †Organic Materials Laboratory, Department of Chemistry, Indian Institute of Technology Roorkee, Roorkee-247 667, India.
authors.forename: Rajendra Kumar
authors.initials: RK
authors.lastname: Konidena
authors.affiliation: †Organic Materials Laboratory, Department of Chemistry, Indian Institute of Technology Roorkee, Roorkee-247 667, India.
authors.forename: K R Justin
authors.initials: KR
authors.lastname: Thomas
authors.affiliation: ‡Department of Material Science and Engineering, National Tsing Hua University, Hsinchu 30013, Taiwan.
authors.forename: Sudhir
authors.initials: S
authors.lastname: Kumar
authors.affiliation: ‡Department of Material Science and Engineering, National Tsing Hua University, Hsinchu 30013, Taiwan.
authors.forename: Ya-Chi
authors.initials: YC
authors.lastname: Wang
authors.affiliation: ‡Department of Material Science and Engineering, National Tsing Hua University, Hsinchu 30013, Taiwan.
authors.forename: Chieh-Ju
authors.initials: CJ
authors.lastname: Li
authors.affiliation: ‡Department of Material Science and Engineering, National Tsing Hua University, Hsinchu 30013, Taiwan.
authors.forename: Jwo-Huei
authors.initials: JH
authors.lastname: Jou