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Novel expanded porphyrazines comprising o- and p-phenylene units were synthesized from self-condensation reactions of acyclic [2+1]-type precursors prepared from 1,3-diiminoisoindoline and the corresponding phenylenediamines. Möbius and Hückel topological structures of [4+2]-type and [3+2]-type expanded porphyrazines, respectively, were elucidated by X-ray crystallography. Despite the Möbius and Hückel [4 n]π-electron systems, these expanded porphyrazines are virtually nonaromatic as a result of their flexible structures in solution, which may diminish intrinsic aromaticity and antiaromaticity. [ABSTRACT FROM AUTHOR]

A novel pyrrolopyrrole azadipyrrin (Janus-PPAD) with Janus duality was synthesized by a Schiff base-forming reaction of diketopyrrolopyrrole. The orthogonal interactions of the hydrogen-bonding ketopyrrole and metal-coordinating azadipyrrin moieties in Janus-PPAD enabled the metal ions to be arranged at regular intervals: zinc(II) and cobalt(II) coordination provided metal-coordinated Janus-PPAD dimers, which can subsequently form hydrogen-bonded one-dimensional arrays both in solution and in the solid state. The supramolecular assembly of the zinc(II) complex in solution was investigated by 1 H NMR spectroscopy based on the isodesmic model, in which a binding constant for the elongation of assemblies is constant. Owing to the tetrahedral coordination, in the solid state, the cobalt(II) complex exhibited a slow magnetic relaxation due to the negative D value of -27.1 cm -1 with an effective relaxation energy barrier U eff of 38.0 cm -1 . The effect of magnetic dilution on the relaxation behavior is discussed. The relaxation mechanism at low temperature was analyzed by considering spin lattice interactions and quantum tunneling effects. The easy-axis magnetic anisotropy was confirmed, and the relevant wave functions were obtained by ab initio CASSCF calculations., (© 2021 Wiley-VCH GmbH.)

A bright near-infrared (NIR) fluorescent molecule was developed based on the donor-acceptor-donor (D-A-D) approach using an aza-BODIPY analog called pyrrolopyrrole aza-BODIPY (PPAB) as an electron-accepting chromophore. Directly introducing electron-donating triphenylamine (TPA) to develop a D-A-D structure caused redshifts of absorption and emission of PPAB into the NIR region with an enhanced fluorescence brightness of up to 5.2×10 4  m -1  cm -1 , whereas inserting a phenylene linker between the TPA donor and the PPAB acceptor induced solvatochromic behavior in emission. Transient absorption spectra and theoretical calculations revealed the presence of a highly emissive hybridized locally excited and charge-transfer state in the former case and the contribution of the dark charge-separated state to the excited state in the latter case. The bright D-A-D PPAB as a novel emitter resulted in a NIR electroluminescence with a high external quantum efficiency of 3.7 % and a low amplified spontaneous emission threshold of ca. 80 μJ cm -2 , indicating the high potential for NIR optoelectronic applications., (© 2021 Wiley-VCH GmbH.)

Efficient electrogenerated chemiluminescences (ECLs) of three pyrrolopyrrole aza-BODIPYs in the near-infrared region by using tripropylamine as a coreactant are reported. Kinetic analysis based on Marcus theory indicates the direct formation of S 2 and T 2 states through the electron transfer reaction, which affects the ECL efficiencies.

Pyrene-bridged boron subphthalocyanine dimers were synthesized from a mixed-condensation reaction of 2,7-di-tert-butyl-4,5,9,10-tetracyanopyrene and tetrafluorophthalonitrile, and their syn and anti isomers arising from the result of connecting two bowl-shaped boron subphthalocyanine molecules were successfully separated. Expansion of the conjugated system of boron subphthalocyanine through a pyrene bridge caused a redshift of the Q band absorption relative to the parent pyrene-fused monomer, whereas combining the curved π-conjugation of boron subphthalocyanine with the planar π-conjugation of pyrene enabled facile embracement of C60 molecules, owing to the enhanced concave-convex π-π stacking interactions., (© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)