A new family of unsymmetrical β-TPA appended ‘push–pull’ porphyrins has been synthesized in good yield for the first time. They exhibited red shifted broad absorption spectral features with high dipole moments and tunable redox properties.

b-Tetra/octa-phenylethynyl substituted porphyrins and their metal (Co(II), Ni(II), Cu(II) and Zn(II)) complexes have been synthesized and characterized. H 2 TPP(PE) 8 exhibited a remarkable red shift in the Soret (Dl max ¼ 92 nm) band and longest wavelength band, Q x (0,0) (Dl max ¼ 117 nm), as compared to H 2 TPP. Interestingly, MTPP(PE) 8 exhibited a 450-500 mV anodic shift in the first ring reduction potentials as compared to MTPP which is ascribed to the electron accepting nature of phenylethynyl groups and extended p-conjugation whereas the first ring oxidation potentials remain unaltered. Hence, we observed a significant reduction in the HOMO-LUMO gap. The fluorescence quantum yields and lifetime values of the free base and Zn(II) porphyrins are found to be 10-20 and 2-6 times, respectively lower than MTPPs. These porphyrins display a strong solvatochromism that is reflected by a large red-shift in their absorption and emission maxima upon increasing the solvent polarity. These porphyrins exhibited lower radiative rate constants (k r ) and enhanced nonradiative rate constants (k nr ) as compared to MTPPs. The decrement in fluorescence lifetime values, quantum yields, radiative rate constants (k r ) and profound solvatochromism with enhanced nonradiative rate constants (k nr ) have been interpreted in terms of intramolecular charge transfer (ICT) from the porphyrin core to phenylethynyl moieties and extended p-conjugation. Further, ZnTPP(PE) 8 was utilized for the colorimetric "naked-eye" sensing of CN À , F À , Cl À , Br À , H 2 PO 4 À and CH 3 COO À ions through axial coordination of anions to Zn(II) metal centre. The electron deficient nature of the Zn(II) centre of ZnTPP(PE) 8 was further proved by axial ligation studies with anions in toluene.ZnTPP(PE) 8 exhibited extremely high binding constants (10 12 to 10 7 M À2 ) with anions. † Electronic supplementary information (ESI) available: Fluorescence, 1 H NMR and MALDI-TOF mass spectra, cyclic voltammograms, HOMO-LUMO diagrams, solvent dependent UV-visible and uorescence spectral proles, UV-Vis spectral titrations of ZnTPP(PE) 8 with different anions. See

β-Octasubstituted porphyrins having three different substituents (Ph, Br and NO2) have been synthesized. They exhibited highly red-shifted absorption spectral features with tunable redox properties leading to a very low HOMO–LUMO gap as compared to MTPPs.

Three new 'push-pull' A 3 B Zn(II)porphyrin dyes having mesopyrenyl, carbazolyl and phenothiazine as electron donors (A) and phenylcarboxylic acid as acceptor/anchor (B) were synthesized and utilized for DSSC application. The spectral and electrochemical redox properties of these new dyes were studied and compared with trans-A 2 BC Zn(II) porphyrin dyes under similar experimental conditions. Red-shifted, broadened absorption peaks, lower fluorescence quantum yields, and shortened lifetimes were observed for the A 3 B dyes as compared to zinc tetraphenylporphyrin control, ZnTPP. DFT optimized structures suggested effective charge separation related to enhanced charge injection efficiency. Driving force for electron injection (ΔG inj ) and dye regeneration (ΔG reg ) calculated from the spectral and electrochemical studies predicted facile electron injection from excited dye into semiconductor TiO 2 in the constructed solar cells. Phenothiazine appended dye (KP-TriPTZ-Zn) showed the highest η value of 7.3 % for PCE with greater J sc and V oc values due to its better light harvesting ability and reduced dye aggregation as compared to other dyes. Our studies demonstrate that the dyes having multiple electron-donating groups exhibit higher photon-to-current conversion efficiency.[a] Dr.

A persubstituted porphyrin with eight entities of triphenylamines at the β-pyrrole positions of a zinc tetraphenylporphyrin, 1, was newly synthesized and characterized. Due to the severe nonplanar distortion caused by the peripheral, electron rich substituents, the zinc porphyrin was able to comfortably bind a relatively large endohedral fullerene, Sc3N@C80, to form a new class of donor–acceptor-type host–guest complex. Spectral, computational, and electrochemical studies were systematically performed to evaluate the binding, spatial geometry, and redox properties of the host–guest system. Further, free-energy calculations were performed to seek the thermodynamic feasibility of excited state charge transfer. Finally, transient absorption spectral studies at different time scales were performed to secure evidence and kinetic information on excited state charge transfer leading to the 1 •+ :Sc3N@C80 •– charge separated species. The present unprecedented, highly functionalized material with electron rich substituents carries zinc porphyrin as a photoactive host to large endohedral fullerenes, and its ability to undergo excited state electron transfer opens up new avenues to build photoactive host–guest systems relevant to light energy conversion and optoelectronic applications.