Protonation-Gated Dual Photochromism of a Chromene-Styryl Dye Hybrid

A novel hybrid bisphotochromic system involving a chromene residue and a styryl dye fragment is described. Initially, the compound shows almost no photochromism due to intramolecular energy and electron transfer between the chromophores. Protonation of the hybrid system blocks the transfer processes and unlocks a dual photochromic activity that includes ring opening of the chromene fragment and E-Z-isomerization of the styryl dye residue. Deprotonation of any photoinduced form resets the system to the initial photoinactive form. © 2017 American Chemical Society

Isomeric commo-Ferracarboranes: meso-, dd/ll-[PPh3R][commo-Fe(2,4-closo-C2B8H10)2] and Their Bimetal Ferra–Copper Zwitterion Derivatives

The reaction of [Na][C2B8H11] with anhydrous FeCl2 in THF affords a mixture of dd/ll and meso isomers of anionic paramagnetic commo-ferracarborane [Ph3PR][commo-1,1′-Fe(closo-2,4-C2B8H10)2] (meso, R = Me: 1a; meso, Et: 1b; dd/ll, R = Me: 2a; dd/ll, R = Et: 2b) with unusual closo geometry. Both dd/ll and meso isomers were successfully isolated and their structures were determined using single-crystal X-ray diffraction studies. Their paramagnetic properties were confirmed with EPR spectra and their oxidative–reductive properties were investigated using cyclic voltammetry. It was shown that facile dd/ll → meso and meso → dd/ll transformations, leading to equilibrium in CH2Cl2 solution, occur. Quantum-chemical calculations of the isomer-to-isomer transformations were performed. Ferra–copper zwitterionic complexes [3,3′,6,7′-exo-{Ph3PCu}-3,3′,6,7′-(µ-H)4-commo-1,1′-Fe(2,4-C2B8H8)2] and [3,3′,6,6′-exo-{Ph3PCu}-3,3′,6,6′-(µ-H)4-commo-1,1′-Fe(2,4-C2B8H8)2] were synthesized and their structures were determined by single-crystal X-ray diffraction studies. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinhei

Isomeric commo-Ferracarboranes: meso-, dd/ll-[PPh3R][commo-Fe(2,4-closo-C2B8H10)2] and Their Bimetal Ferra–Copper Zwitterion Derivatives

The reaction of [Na][C2B8H11] with anhydrous FeCl2 in THF affords a mixture of dd/ll and meso isomers of anionic paramagnetic commo-ferracarborane [Ph3PR][commo-1,1′-Fe(closo-2,4-C2B8H10)2] (meso, R = Me: 1a; meso, Et: 1b; dd/ll, R = Me: 2a; dd/ll, R = Et: 2b) with unusual closo geometry. Both dd/ll and meso isomers were successfully isolated and their structures were determined using single-crystal X-ray diffraction studies. Their paramagnetic properties were confirmed with EPR spectra and their oxidative–reductive properties were investigated using cyclic voltammetry. It was shown that facile dd/ll → meso and meso → dd/ll transformations, leading to equilibrium in CH2Cl2 solution, occur. Quantum-chemical calculations of the isomer-to-isomer transformations were performed. Ferra–copper zwitterionic complexes [3,3′,6,7′-exo-{Ph3PCu}-3,3′,6,7′-(µ-H)4-commo-1,1′-Fe(2,4-C2B8H8)2] and [3,3′,6,6′-exo-{Ph3PCu}-3,3′,6,6′-(µ-H)4-commo-1,1′-Fe(2,4-C2B8H8)2] were synthesized and their structures were determined by single-crystal X-ray diffraction studies. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinhei