(Invited) 5,15-Diazatetrabenzoporphyrins: Evaluation as Organic Semiconductors

Abstract

Tetrabenzo-5,15-diazaporphyrin (TBDAP) is a structural hybrid molecule of tetrabenzoporphyrin (TBP) and phthalocyanine (Pc). As compared with TBP, TBDAP has energetically lower HOMO and LUMO because of the higher electronegativity of nitrogen atom at meso-position. Moreover, its optoelectronic properties, solubility and molecular arrangement in the solid state can be controlled by introducing various substituents at another meso-carbons. These electronic and structural tunabilities of TBDAP are advantageous to the organic electronic application such as organic field-effect transistors (OFETs) and organic photovoltaics (OPVs), but selective and efficient synthetic methods for TBDAP are limited. Triisopropylsilyl (TIPS)-ethynyl group is one of the most popular substituents for organic semiconducting molecules. We synthesized 5,15- bis(triisopropylsilylethynyl)tetrabenzoporphine (TIPS-TBP) and its metal complexes. TIPS-TBP has reasonable solubility for solution-processed OFETs and exhibits excellent hole mobilities of 1.1 cm2 V− 1 s− 1 and 2.16 cm2 V− 1 s− 1 in dip-coating FET and single-crystal FET, respectively [1, 2]. These values are higher than that of pristine free-base TBP (0.07 cm2 V−1 s−1), indicating that TIPS-ethynyl group is also useful for porphyrin analogues. Herein, we report the synthesis of 10,20-bis(triisopropylsilylethynyl)tetrabenzo-5,15-diazaporphine (TIPS-TBDAP) by metal-template aza-annulation reaction [3,4]. TIPS-TBDAP exhibited efficient far-red fluorescence in solution and formed one-dimensional (1D) columnar structure in crystal packing. Its charge transporting property evaluated by preparing dip-coating FET and single-crystal FET will be also reported.