Synthesis, structures and charge-transfer complexations of 1,n-di-[3,6-di-(9-carbazolyl)-9-carbazolyl]alkanes with tetracyanoethylene and tetranitromethane
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Synthesis and charge-transfer (CT) complexations of amorphous 3,6-di-(9-carbazolyl)-9-ethylcarbazole, 3,6-di-(9-carbazolyl)-9-hexylcarbazole and a series of 1,n-di-[3,6-di-(9-carbazolyl)-9-carbazolyl]alkanes (n = 15) with electron acceptors tetracyanoethylene and tetranitromethane are reported. The molar extinction coefficients (epsilon), equilibrium constants (K-eq), enthalpies (Delta H) and entropies (Delta S) of complexations have been determined. The low K-eq values (1.833.82 M-1 for carbazole-TCNE and 0.280.45 M-1 for carbazole-TNM complexes) show weak donor-acceptor associations. The negative values of Delta H determined to be between -2.09 +/- 0.08 and -3.10 +/- 0.21 kcal mol(-1) for carbazole-TCNE complexes and -0.91 +/- 0.08 and -3.31 +/- 0.28 kcal mol(-1) for carbazole-TNM complexes indicate that complexations are driven by the exothermic enthalpies. Computational analysis using semi-empirical and DFT methods were applied to clarify the structures of the synthesized molecules and the nature of their CT complexations.