Indolo[3,2-b]carbazole-based poly(arylene vinylene)s. The influence of substitution position on spectroscopic and electrochemical properties

Three novel soluble poly(arylene vinylene)s containing indolo[3,2-b]carbazole moiety inserted in the polymer chain at 2,8-, 3,9- and 6,12-positions were synthesized and used to study the influence of the linking topology on the optical and electronic properties. The new polymers were obtained through a palladium-catalysed cross-coupling Stille reaction between bis-bromine[3,2-b]indolocarbazoles and trans-1,2-bis(tributylstannyl)ethane in toluene. Polymers were soluble in chlorinated, aromatic and aprotic polar solvents. The structures of polymers were investigated using Fourier transform infrared, H-1 NMR and C-13 NMR spectroscopies. The number-average molecular weights determined using gel permeation chromatography are in the range (6.3-9.4) x 10(3) g mol(-1) while thermogravimetric analysis showed the polymers to possess high thermal stability. UV-visible and emission spectroscopy evidenced a bathochromic shift of (max) for indolocarbazole linking topology in the polymer backbone, in the order: 6,12 < 2,8 < 3,9. Electrochemical properties were investigated by cyclic voltammetry using thin films cast on platinum disc working electrodes and highest occupied and lowest unoccupied molecular orbital energy levels were determined. (c) 2016 Society of Chemical Industry