Search for: All records

A sterically strained 32π‐electron antiaromatic bis‐BODIPY macrocycle in which two BODIPY fragments are linked byp‐divinylbenzene groups was prepared and characterized. Unlike regular BODIPYs, the fluorescence in this macrocycle is quenched. The broad signals in the NMR spectra of the macrocycle were explained by the vibronic freedom of thep‐divinylbenzene fragments. The possible diradicaloid nature of the macrocycle was excluded on the basis of variable‐temperature EPR spectra in solution and in solid state, which is indicative of its closed‐shell quinoidal structure. Themeso‐C−H bond in the macrocycle and its precursor BODIPY dialdehyde3forms a weak hydrogen bond with THF and is susceptible for the nucleophilic attack by organic amines and cyanide anion. The reaction products of such a nucleophilic attack havemeso‐sp³carbon atoms and were characterized by NMR, mass spectrometry and, in one case, X‐ray crystallography. Unlike the initial bis‐BODIPY macrocycle, the adducts have strong fluorescence in the 400 nm region. The electronic structure and spectroscopic properties of new chromophores were probed by density functional theory (DFT) and time‐dependent DFT (TDDFT) calculations and correlate well with the experimental data.

 

The electronic communication between two ferrocene groups in the electron-deficient expanded aza-BODIPY analogue of zinc manitoba-dipyrromethene (MB-DIPY) was probed by spectroscopic, electrochemical, spectroelectrochemical, and theoretical methods. The excited-state dynamics involved sub- ps formation of the charge-separated state in the organometallic zinc MB-DIPYs, followed by recovery of the ground state via charge recombination in 12 ps. The excited-state behavior was contrasted with that observed in the parent complex that lacked the ferrocene electron donors and has a much longer excited-state lifetime (670 ps for the singlet state). Much longer decay times observed for the parent complex without ferrocene confirm that the main quenching mechanism in the ferrocene-containing 4 is reflective of the ultrafast ferrocene-to-MB-DIPY core charge transfer (CT 

The preparation of radicals with intense and redox‐switchable absorption beyond 1000 nm is a long‐standing challenge in the chemistry of functional dyes. Here we report the preparation of a series of unprecedented stable neutral nickel(II) and copper(II) complexes of “Manitoba dipyrromethenes” (MB‐DIPYs) in which the organic chromophore is present in the radical‐anion state. The new stable radicals have an intense absorption atλ_max∼1300 nm and can be either oxidized to regular [M^II(MB‐DIPY)]⁺(M=Cu or Ni) or reduced to [M^II(MB‐DIPY)]⁻compounds. The radical nature of the stable [M^II(MB‐DIPY)] complexes was confirmed by EPR spectroscopy with additional insight into their electronic structure obtained by UV‐Vis spectroscopy, electro‐ and spectroelectrochemistry, magnetic measurements, and X‐ray crystallography. The electronic structures and spectroscopic properties of the radical‐based chromophores were also probed by density functional theory (DFT) and time‐dependent DFT (TDDFT) calculations. These nickel(II) and copper(II) complexes represent the first stable radical compounds with a MB‐DIPY ligand.

 

A one‐step synthetic pathway for the preparation of fully conjugated β‐isoindigo‐azaDIPY hybrid chromophores comprised of β‐isoindigo and azadipyrromethene moieties is reported. The target compounds were characterized by spectroscopic, crystallographic, and theoretical methods and show unprecedented broad absorption across the visible region of the electromagnetic spectrum. The X‐ray crystal structure of the octa(n‐butyl)‐β‐isoindigo‐azaDIPY derivative revealed that a trans‐configuration of the β‐isoindigo fragment accompanies a planar conjugated core.

 

A one‐step synthetic pathway for the preparation of fully conjugated β‐isoindigo‐azaDIPY hybrid chromophores comprised of β‐isoindigo and azadipyrromethene moieties is reported. The target compounds were characterized by spectroscopic, crystallographic, and theoretical methods and show unprecedented broad absorption across the visible region of the electromagnetic spectrum. The X‐ray crystal structure of the octa(n‐butyl)‐β‐isoindigo‐azaDIPY derivative revealed that a trans‐configuration of the β‐isoindigo fragment accompanies a planar conjugated core.