Janus Pyrrolopyrrole Aza-dipyrrin: Hydrogen-Bonded Assemblies and Slow Magnetic Relaxation of the Cobalt(II) Complex in the Solid State.

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 Ueff 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.

Pyrrolopyrrole Aza-BODIPY Analogues as Near-Infrared Chromophores and Fluorophores: Red-Shift Effects of Substituents on Absorption and Emission Spectra.

Pyrrolopyrrole aza-BODIPY analogues (PPABs) are a new class of UV/vis and near-infrared chromophores. Varying the substituents results in red-shifts of both the absorption and emission spectra. Extension of the lengths of the oligothiophene substituents from thiophene to quaterthiophene caused red-shifts of the absorption and emission from 699 and 712 nm to 809 and 853 nm, respectively. The piperidylthiophene-substituted PPAB exhibited similar red-shifts of the absorption and emission to 810 and 831 nm, respectively, although only a single thienyl component is present, because of the strong electron-donating nature of the piperidine substituent.