Recent advances in subphthalocyanines and related subporphyrinoids

Subporphyrinoids constitute a class of extremely versatile and attractive compounds. Herein, a comprehensive review of the most recent advances in the fundamentals and applications of these cone-shaped aromatic macrocycles is presented.

Dephosphinylative [4 + 2] Benzannulation of Phosphinyl Ynamines: Application to the Modular Synthesis of Polycyclic Aromatic Amines

A series of 9-amino-10-halophenanthrenes were synthesized through a one-pot process, including dephosphinylative Sonogashira-Hagihara coupling of 2-bromobiphenyls with air-stable phosphinyl ynamines, followed by halonium-promoted [4 + 2] benzannulation of the resulting 2-(aminoethynyl)biphenyls. Nonsubstituted and methyl-substituted 2-bromobiphenyls rapidly underwent the Sonogashira-Hagihara aminoethynylation and the halogenative Friedel-Crafts benzannulation to provide the corresponding amino(halo)phenanthrenes in high yields, while electron-sufficient and -deficient substrates did slowly undergo the former and the latter to result in low yields, respectively. This protocol worked well for the syntheses of highly π-extended aminophenanthrenes and aminobenzonaphthothiophenes with different optical properties. Further application of this approach between 2,2″- and 2',5'-dibromo-p-terphenyls with phosphinyl ynamines led to the regioselective formation of 6,13-diamino-5,12-dihalo- and 5,12-diamino-6,13-dihalo-dibenz[a,h]anthracenes via dual aminoethynylation and [4 + 2] benzannulation. The obtained analogues showed different ultraviolet-visible absorption and photoluminescence spectra with different emission quantum yields in CH₂Cl₂ solution and the powder state.

Photoactive preorganized subphthalocyanine-based molecular tweezers for selective complexation of fullerenes

The development of new chromophoric receptors capable of binding curved carbon nanostructures is central to the quest for improved fullerene-based organic photovoltaics. We herein report the synthesis and characterization of a subphthalocyanine-based multicomponent ensemble consisting of two electron-rich SubPc-monomers rigidly attached to the convex surface of an electron-poor SubPc-dimer. Such a unique configuration, especially in terms of the two SubPc-monomers, together with the overall stiffness of the linker, endows the multicomponent system with a well-defined tweezer-like topology to efficiently embrace a fullerene in its inner cavity. The formation of a 1 : 1 complex was demonstrated in a variety of titration studies with either C60 or C70. In solution, the underlying association constants were of the order of 105 M-1. Detailed physicochemical experiments revealed a complex scenario of energy- and electron-transfer processes upon photoexcitation in the absence and presence of fullerenes. The close proximity of the fullerenes to the electron-rich SubPcs enables a charge shift from the initially formed reduced SubPc-dimer to either C60 to C70.

Fluorinated boron subphthalocyanines: Lewis acid based templating chemistry facilitates random halide exchange, and fluoride versus chloride affects the basic photophysical properties and the solid-state arrangement

A sub-group of the phthalocyanine family, the boron subphthalocyanines (BsubPcs), have robust chemistry and can be readily modified at the axial and peripheral positions to tune their physical properties.

Trifluoroethoxy-Coated Subphthalocyanines Attract Small Arenes in Their π-Concave Cavity

X-ray crystallographic analyses of a series of trifluoroethoxy-substituted subphthalocyanines disclosed that a molecule of toluene is clasped at the center of the molecular concave cavity. Twelve trifluoroethoxy substituents, which flexibly surround the toluene molecule to hold it on the 14 π-electron-conjugated surface of the subphthalocyanines, can also catch a molecule of benzene. In contrast, a nonsubstituted subphthalocyanine does not show the same phenomena, and two subphthalocyanine units are required to maintain a small aromatic compound in their concave cavity. DFT calculations of the complexes were conducted to better understand the arene clathrates. Trifluoroethoxy-substituted subphthalocyanines can be used to prepare arene clathrates as a result of their concave space. This is a unique approach to obtaining X-ray crystal structures of small noncrystalline aromatic compounds.

Synthesis and application of trifluoroethoxy-substituted phthalocyanines and subphthalocyanines

Phthalocyanines and subphthalocyanines are attracting attention as functional dyes that are applicable to organic solar cells, photodynamic therapy, organic electronic devices, and other applications. However, phthalocyanines are generally difficult to handle due to their strong ability to aggregate, so this property must be controlled for further applications of phthalocyanines. On the other hand, trifluoroethoxy-substituted phthalocyanines are known to suppress aggregation due to repulsion of the trifluoroethoxy group. Furthermore, the electronic characteristics of phthalocyanines are significantly changed by the strong electronegativity of fluorine. Therefore, it is expected that trifluoroethoxy-substituted phthalocyanines can be applied to new industrial fields. This review summarizes the synthesis and application of trifluoroethoxy-substituted phthalocyanine and subphthalocyanine derivatives.

Trifluoroethoxy-Coated Subphthalocyanine affects Trifluoromethylation of Alkenes and Alkynes even under Low-Energy Red-Light Irradiation

Photoredox chemical reactions induced by visible light have undergone a renaissance in recent years. Polypyridyl dyes such as Ir(ppy)3 and Ru(bpy)3 are key catalysts in this event, and blue- or white-light irradiation is required for the chemical transformations. However, it remains a challenge to achieve reactions under the lower energy of red light. We disclose, herein, that trifluoroethoxy-coated subphthalocyanine realizes the red-light-driven trifluoromethylation of alkenes and alkynes with trifluoromethyl iodide in good-to-high yields. Perfluoroalkylations were also achieved under red light. The reaction mechanism is discussed with the support of UV/Vis spectroscopy and cyclic voltammetry of trifluoroethoxy-coated subphthalocyanine. Light irradiation/dark study also supports the proposed mechanism.

Synthesis and electronic properties of nitrogen-bridged dimers of boron subphthalocyanines

We describe for the first time the synthesis and characterization of a new family of subphthalocyanine derivatives, the μ-azo dimers, in which two closely interacting macrocycles are axially linked together by a B–N–B bridge.