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A diradical/biradical character of organic derivatives is one of the key aspects of contemporary research focusing on the fundamental studies followed by potential applicability relying on the unique optical, electronic, or magnetic properties assigned to unpaired electrons. A precise involvement of two p‐phenylenes into a cyclophane‐like conjugated, diatropic system creates a flexible molecule with the two different characters of both subunits (benzene and quinone) imprinting into the structure a Kekulé delocalized system. A dynamic of both carbocyclic subunits, and their mutual interaction generates a singlet open‐shell state (J=−1.25 kcal/mol) as documented spectroscopically (NMR and EPR). The extended theoretical analysis has proved a correlation between dihedral angle and the diradicaloid character that shifts from a closed‐shell singlet to an open‐shell state, eventually showing the y0=0.86 for 78 degrees and ΔEST=−0.34 kcal/mol. [ABSTRACT FROM AUTHOR]

Porphyrinoid macrocycles are unbreakably linked with the coordination of central cations that drastically influence the observed behavior. A specific place has been recorded for structures where more than one cation is entrapped in a single macrocycle. It has been a characteristic feature of expanded porphyrinoids where the increased coordination space allows a multiple coordination. Because of specific steric confinements, an incorporation of more than one cation within regular or contracted porphyrinoids is more demanding but it can be realized on several ways significantly modifying the observed behavior. We will discuss synthetic strategies leading to structures with increased number of cations and the influence on the observed behavior of such modification. [ABSTRACT FROM AUTHOR]

π-Extended and strongly coupled chromophores are constantly explored because of their potential for finding a place in many fields of research focusing on both aspects – the fundamental knowledge and the application studies. The synthetic approach leading to controlled formation of porphyrinoid system with two coordination cores shows an alternative way for controlling the delocalization within the extended π-system. It drastically influences the optic response which after a basic initiator (reversibly) shifts the absorbance to the red region following the significant planarization that increases observed communication between two subunits. Even deeper modification can be done within the system by doping the obtained structure with boron(III) that in addition introduces another switching factor based on Lewis acidity of the introduced metalloid. [ABSTRACT FROM AUTHOR]

Insertion of PCl3 or PhBCl2 into 5,10,15,20‐tetraaryl‐p‐benziporphyrin prompted an intramolecular fusion affording anti‐aromatic phosphorus(V) and non‐aromatic boron(III) complexes of two N‐fused dihydro‐p‐benziporphyrin isomers. These macrocycles are classified as carbatriphyrin due to the common [CNN] coordination. A sequence of direct transformations, triggered by protonation or two‐electron redox processes, afforded a set of three mutually convertible N‐fused p‐benziporphyrinoids, with distinct anti‐aromatic, non‐aromatic, and aromatic spectroscopic features. It′s as simple as 1, 2, 3! p‐Benziporphyrin undergoes deep structural modifications induced by the coordination of boron(III) or phosphorus(V), forming N‐fused p‐benziporphyrinoids which imprint a carbatriphyrin(3.1.1) motif. A distinctive structural frame of contracted carbaporphyrinoid creates a three‐level aromaticity switching system. [ABSTRACT FROM AUTHOR]

The structurally prearranged carbaporphyrins 22-methyl- and 22-ethyl- m-benziporphyrins provide the platform stabilizing aromatic rhodium(III) 22-(μ-methylene- m-benziporphyrin) and rhodium(III) 22-(μ-ethylidene- m-benziporphyrin). An intramolecular conversion facilitated by the m-phenylene reactivity and observed for both aromatic complexes efficiently leads to rhodium(III) 21-(μ-methylene)-21-carbaporphyrin and rhodium(III) 21-(μ-ethylidene)-21-carbaporphyrin. The distinctive macrocyclic environment of rhodium(III) 21-carbaporphyrin created an opportunity to trap unique organometallic transformations of inner core substituents affording the fulvene-like bond pattern or the rearrangement to 21-vinyl substituent. The one-electron reduction of the rhodium(III) carbaporphyrin anion π-radical with a (d xy)2(d xz)2(d yz)2-(P.−) electronic configuration is demonstrated. The further process of reduction of paramagnetic species triggers the ethyl migration from carbon(22) to rhodium(III), affording the diamagnetic rhodium(III) meta-benziporphyrin containing the apically coordinated σ-ethyl ligand providing an example of reversible C(sp2)−C(sp3) bond cleavage. [ABSTRACT FROM AUTHOR]

A structurally prearranged carbaporphyrin, 22-methyl- m-benziporphyrin, provided the perfect macrocyclic platform to form gold(III) 22-methyl- m-benziporphyrin, which facilitates the specific m-benzene ring contraction yielding gold(III) 21-methyl 21-carbaporphyrin with remarkably high yield. [ABSTRACT FROM AUTHOR]