Boron subphthalocyanines (SubPcs) are attractive as light harvesting materials in photovoltaic devices. Here we present the synthesis, optical and electrochemical properties, and device performances of a series of donor−acceptor‐functionalized SubPc derivatives incorporating a carboxylic acid for anchoring onto TiO2. Liquid‐ and solid‐state dye‐sensitized solar cells (DSCs) were prepared from three compounds, and a triad system consisting of two aniline donor moieties and a benzothiadiazole acceptor moiety was found to exhibit the highest power conversion efficiency (PCE) in the series (PCE=1.54 %; solid‐state device). The compounds were prepared by stepwise acetylenic coupling reactions. In addition, we present the synthesis and optical properties of a SubPc derivative incorporating three anilino‐substituted 1,1,4,4‐tetracyanobutadiene units, prepared by the [2+2] cycloaddition between three ethynyl units at the SubPc periphery and three tetracyanoethylene molecules followed by electrocyclic ring‐opening reactions.

A series of boron subphthalocyanine-tetracyanobutadiene-ferrocene (SubPc-TCBD-Fc) triads was synthesized by subjecting SubPcs with a ferrocenylethynyl substituent at either the axial or peripheral position to a [2 + 2] cycloaddition reaction with tetracyanoethylene followed by retroelectrocyclization. The ferrocenylethynyl unit was introduced at the axial position (at the boron atom) by a simple aluminum chloride-mediated alkynylation reaction, while functionalization at the SubPc periphery was accomplished by a Sonogashira coupling reaction. The conversion of one alkyne unit into a TCBD unit in combination with the location of the resulting TCBD-Fc moiety was found to have a strong influence on the optical and redox properties, which is ascribed to very different ground-state interactions between the individual donor/acceptor systems. The first electrochemical oxidation could thus be anodically shifted by as much as 0.4 V from the strongest donor molecule (with most unperturbed ferrocene character) to the poorest donor molecule (with strongly perturbed ferrocene character). Six redox states could be reached reversibly for the SubPc-TCBD-Fc triads, -3, -2, -1, 0, + 1, + 2, and for one compound the formation of a tetraanion persistent at the time scale of slow scan voltammetry was observed.

The very limited class of fluorophores, with a long fluorescence lifetime (>10 ns) and fluorescence beyond 550 nm, has been expanded with two benzo-fused triangulenium derivatives and two cationic [5]-helicene salts. The syntheses of the benzo-bridged dioxa-and diazatriangulenium derivatives (BDOTA + and BDATA + , respectively) required two different synthetic approaches, which reflect the structural and physiochemical impact on the reactivity of [5]-helicenium precursors. Spectroscopic investigations show that the introduction of the benzo bridge into the triangulenium chromophore significantly redshifts the absorption and emission while maintaining fluorescence lifetimes above 10 ns. The combination of a high quantum yield, long fluorescence lifetime, and emission above 600 nm is possible only if the structural aspects of the triangulenium framework are perfectly harmonized to secure a low rate of nonradiative deactivation. The new benzo bridge may be a general motif to obtain red-shifted derivatives of other dye classes.

Boron subphthalocyanines comprised of three isoindole units bridged by aza-linkages are attractive light harvesters on account of their intense low-energy absorptions. Herein, we present a class of related compounds, in which one or two isoindole units are substituted for thieno[3,4-c]pyrrole units - thieno-fused subporphyrazines. Such changes have remarkable consequences for the optical properties, as was revealed by combined experimental and theoretical studies. Thus, we find that the lowest-energy absorptions cover a much broader region with a significantly redshifted end-absorption and without compromising the absorption intensities. Thieno-fused subporphyrazines also underwent more readily oxidation and reduction, indicating an increased HOMO energy and decreased LUMO energy. In addition, they were found to readily co-crystallize with Buckminsterfullerene, C . Altogether, these findings render this new class of chromophores attractive candidates for light-harvesting applications.

Tweezer-like molecules comprised of two boron subphthalocyanine (SubPc) units were prepared by Sonogashira couplings and investigated using NMR spectroscopy for their ability to bind fullerenes (C and C). The preorganization of the tweezers provided association constants of ca. 10 M in toluene- d, while a SubPc monomer did not show any association. Nevertheless, the SubPc monomer crystallized with the fullerenes as 2:1 complexes, supporting the favorable tweezer-like design for complexation, which was further corroborated by computations.