Photoisomerization of Enediynyl Linker Leads to Slipped Cofacial Hydroporphyrin Dyads with Strong Through-Bond and Through-Space Electronic Interactions.

Photoisomerization of 3,4-di(methoxycarbonyl)-enediyne linker in hydroporphyrin (chlorin or bacteriochlorin) dyads leads to thermally stable cis isomers, where macrocycles adopt a slipped cofacial mutual geometry with an edge-to-edge distance of ∼3.6 Å (determined by density functional theory (DFT) calculations). Absorption spectra exhibit a significant splitting of the long-wavelength Q band, which indicates a strong electronic coupling with a strength of V = ∼477 cm that increases to 725 cm upon metalation of hydroporphyrins.

Photochemical rearrangement of calix[4]arene-derived bis(spirodienones): formation of a new macrocycle.

Bis(spirodienones) of calix[4]arene undergo a facile photochemical rearrangement leading to a new macrocycle having a spirocyclic cyclopentenone-THF unit, a trisubstituted phenol, and a benzofuran moiety. The macrocyclic ring system has a 14-membered irregular cavity and resembles a partial bowl in the solid state.