Three-Step Synthesis and Absorption and Emission Properties of Peripherally Peralkynylated Tetrapyrazinoporphyrazines

Peripheral alkynyl substitution of strongly absorbent chromophores, among them porphyrins1 and the phthalocyanines,2 is becoming an increasingly popular strategy for the design of functional dyes and molecular devices. The interest in structural modifications of this kind arises mainly from two factors. First, the acetylenic units enlarge the π-systems of the chromophores and induce bathochromic shifts in the electron absorption and emission spectra. Second, terminal alkynyl groups can be invoked to serve as covalent linkers for the assembly of delocalized multichromophor chains or two-dimensional polymer networks. Although peralkynylation of a given chromophor is often hampered by the tedious preparation of suitable precursors,2a a lower degree of alkynyl substitution frequently results in the formation of a mixture of regioisomers. We have therefore explored the possibility of employing small acetylenic building blocks for the rapid assembly of alkynylated chromophores. We report herein a short synthesis of 2,3,9,10,16,17,23,24-octalkynyl tetrapyrazinoporphyrazines3 (TPyPors) 1 from oxalyl chloride, along with some of the optical properties associated with the 72 π-electrons of 1.