A series of rhenium(i) dipyrrinato complexes (Re1–Re8) have been prepared and characterized; their crystal structures, phosphorescence and singlet oxygen generation studies are reported.

meso-Substituted BODIPY with N-butylcarbazole () was prepared and derivatized. Dibromo BODIPY , α-formyl BODIPY and β-formyl BODIPY were synthesized. All compounds were characterized by HRMS, NMR, UV-vis absorption, electrochemical and fluorescence techniques. The crystal structures of BODIPY and its dibromo derivative were also solved. In both the X-ray structures, the dihedral angle between the meso-carbazole group and the dipyrrin plane was decreased, suggesting the increased interaction between the two units. meso-Substitution with the N-butylcarbazole group on the BODIPY core rendered huge Stokes shifts (111-168 nm) and higher quantum yields as compared to meso-aryl BODIPY. An efficient energy transfer from the carbazole unit to the BODIPY core was observed by fluorescence spectroscopy for all the compounds . CV studies of compounds showed anodic shifts of the reduction and oxidation potentials, suggesting that the meso-carbazole group is affecting the electronic properties of the BODIPY core and making them easier to reduce.

Donor–acceptor type pyrene substituted aza-BODIPYs are reported, and efficient energy transfer from pyrene moieties to the aza-BODIPY core caused significant red shifts in their absorption and emission spectra.

A series of bis-BODIPYs 1-6 bridged via thiophene, furan, N-alkylcarbazole, triphenyl-amine, para- and meta-phenylene groups have been synthesized and characterized by various spectroscopic techniques. The change in the spectroscopic properties of bis-BODIPYs upon varying the size of spacers was studied. X-ray crystal structures of three bis-BODIPYs containing triphenylamine, para- and meta-phenylene bridges were solved. Intermolecular C(H)π and ππ stacking interactions were observed in solid state structures of three bis-BODIPYs. The dihedral angles between the spacer unit and two boron-dipyrrin units were lower in all three compounds as compared to their corresponding monomers. This suggests increased interactions between the two boron-dipyrrin units in molecules which are in turn reflected in the anodic shifts in their reduction potentials. DFT studies indicated effective electronic interactions between spacers and two boron dipyrrin units in all the bis-BODIPYs. The calculated HOMO-LUMO gap was found to be lower for bis-BODIPY having bulky carbazole spacers and higher for bis-BODIPY having smaller furan spacers. Changing the spacer size clearly affected the spectroscopic properties of the bis-BODIPYs and red shifted absorption and emission maxima were observed for bis-BODIPYs with furan and thiophene spacers as compared to bis-BODIPYs with phenylene or bulky aromatic spacers.

Pyridylethenyl-substituted N-confused porphyrins (NCPs) were synthesized, and their cis-trans isomerization was studied. Among four possible isomers, trans-3H and cis-2H types of structures, of which aromaticity and absorption/emission properties differ largely, were isolated. The cis-isomer was largely stabilized by the intramolecular hydrogen bonding between the pyrrolic-NH and the pyridinic-N in the vicinity. The thermal cis-trans isomerization proceeded even at 30 °C, which was significantly accelerated by the pyridine added to the system. The kinetic studies revealed that the isomerization reaction was second-order and the activation energy of the thermal isomerization from cis to trans isomer was ΔG = 35.7 kcal/mol at 298 K, which is significantly smaller than that of Ni complex (42.3 kcal/mol). An intermolecular proton transfer induced cis-trans isomerization mechanism was proposed.

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Difluoroboron-dipyrromethenes (BODIPYs) are highly popular fluorescent dyes with applications as NIR probes for bioimaging, fluorescent tags/sensors and as photosensitizers in cancer therapy and organic photovoltaics. This review concentrates on the synthesis and spectral properties of BODIPY dyes conjugated with carbazole heterocycle. The carbazole is an electron rich tricyclic compound and due to its excellent electronic properties, it is extensively used in the production of electroluminescent materials and polymers. This review highlights the recent progress made on the series of BODIPY derivatives containing carbazole ring at alpha, beta, and meso-positions of the BODIPY skeleton. Carbazole based hybrid BODIPYs, carbazole linked aza-BODIPYs and carbazole-fused BODIPYs are also discussed.

Carbazole and p-anisyl substituted BODIPY dyes with a cyanoacetic acid anchoring group have been prepared and their spectral, electrochemical properties and photosensitizing potential in DSSC have been evaluated. X-ray structure of N-phenylcarbazole substituted BODIPY revealed lower torsion angle between BODIPY plane and carbazole plane, suggesting increased communication between the two units. DFT studies indicated effective electronic interactions between the BODIPY unit and carbazole substituents. The N-butylcarbazole and N-phenylcarbazole substituted BODIPYs showed anodic shifts in their reduction potentials, indicating facile reduction process. The predicted HOMO-LUMO gaps are in agreement with the electrochemical result and the lower band gap was observed for the carbazole substituted BODIPYs.