Synthesis, structures and charge−transfer complexations of 1,n-di-[3,6-di-(9-carbazolyl)-9-carbazolyl]alkanes with tetracyanoethylene and tetranitromethane

Abstract

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 = 1–5) with electron acceptors tetracyanoethylene and tetranitromethane are reported. The molar extinction coefficients (ε), equilibrium constants (Keq), enthalpies (ΔH) and entropies (ΔS) of complexations have been determined. The low Keq values (1.83–3.82 M−1 for carbazole−TCNE and 0.28–0.45 M−1 for carbazole−TNM complexes) show weak donor−acceptor associations. The negative values of ΔH 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.