Rahul Soman

Third-order nonlinear optical investigations of meso-tetrakis(2,3,5,6-tetrafluoro-N,N-dimethyl-4-anilinyl)porphyrin and its metal complexes.

We report here the experimental investigation on third-order nonlinear optical parameters of 5,10,15,20-tetrakis(2,3,5,6-tetrafluoro-N,N-dimethyl-4-anilinyl)porphyrin and its various metal complexes, using Z-scan technique at 532 nm. The third-order nonlinear optical susceptibilities (χ(3)) were of the order 10(-12) esu and are compared through degenerate four wave mixing (DFWM). The operating mechanism is reverse saturable absorption (RSA) as the effective excited-state absorption cross-section was found higher than ground state absorption cross-section as well as the magnitude of nonlinear absorption coefficient was found decreasing with on-axis input intensity. The compounds found to exhibit good optical limiting at 532 nm, 7 ns excitation steering applications in laser safety.

Axial ligand modified high valent tin(IV) porphyrins: synthesis, structure, photophysical studies and photodynamic antimicrobial activities on Candida albicans

Herein, we report the synthesis, structure, photophysical properties and photodynamic antimicrobial activities on Candida albicans of axial ligand modified high valent tin(IV) porphyrins, namely SnIV(OH)2T(4-CMP)P (1), SnIV(OH)2T(4-CP)P (2) and SnIV(O-NO2Ph)2T(4-CMP)P (3). The newly synthesized porphyrins were characterized by various spectroscopic methods and single crystal X-ray diffraction analysis. The crystal structures of the precursor porphyrin, SnIV(Cl)2T(4-CMP)P and 3 are well stabilized by various intermolecular interactions and porphyrin 3 shows complementary bonding interactions between the nitro groups (N⋯O) forming a one-dimensional array. The fluorescence lifetime of 3 is lower compared to other porphyrins which indicates that there is a considerable interaction between the tin(IV) porphyrin core and nitrophenyl system and this could be the reason for its significant phototoxicity. This is further evident from X-ray crystallography and DFT calculations. In the presence of light, tin(IV) porphyrins significantly inhibited the growth of C. albicans in liquid as well as in the solid agar medium and the growth inhibitory effects were much less under dark conditions. The porphyrin internalization as well as localization within the Candida cells were examined by fluorescence microscopic analysis. Our results suggest that the mechanism behind the photodynamic inactivation of C. albicans could be through the generation of singlet oxygen species within the cells.

Protonation and axial ligation intervened fluorescence turn-off sensing of picric acid in freebase and tin(IV) porphyrins

Freebase and tin(IV)-porphyrins are examined for the selective detection of picric acid and their affinity is revealed by spectroscopic titrations and X-ray structures. The sensing is mediated through protonation and axial ligation in 1–5 and 6–9 respectively. Fluorescent lifetime studies show that the quenching is dynamic in the freebase and static in tin(IV)-porphyrins.

χ(3) measurements of axial ligand modified high valent tin(IV) porphyrins using degenarete four wave mixing at 532nm

Porphyrins and metalloporphyrins are unique class of molecules for Nonlinear Optical applications because of their unique structure of altering the central metal atom, large extended π-system, high thermal stability, tunable shape, symmetry and synthetic versatility Here, we report χ(3) Measurements of a simple phenyl porphyrins and its highvalent tin(IV) porphyrins with Bromination characterized by UV-Visible spectroscopic method. In this study, we employed the Degenerate Four Wave Mixing technique using forward Boxcar geometry with an Nd:YAG nano second pulsed laser as source and it was found that the tin(IV) porphyrin with Bromination exhibits good χ(3) value and figure of merit.

Synthesis and third order optical investigations of nitrophenyl porphyrins

The third-order nonlinear optical studies of Nitrophenyl Porphyrins using degenerate fourwave mixing has been done. Samples were prepared using standard methods. Study shows that the compounds have high χ3 Values suitable for photonic applications.

CCDC 1041763: Experimental Crystal Structure Determination

Related Article: Rahul Soman, Subramaniam Sujatha and Chellaiah Arunkuma|2016|J.Porphyrins Phthalocyanines|20|833|doi:10.1142/S1088424616501017

Structural elucidation and study of intermolecular interactions in meso-tetratolylporphyrins

Synthesis and crystal structure analysis of meso-tetratolylporphyrins, 1–5 combined with computational Hirshfeld surface analysis were investigated. The crystal packing of porphyrins 1, 3 and 4 are arranged in an “orthogonal fashion” whereas 2 and 5 are in a “slip-stack or off-set fashion” through various intermolecular interactions. Compound 2 exhibits saddle geometry whereas 5 showed a domed geometry as evident from the single crystal X-ray diffraction studies. The enhancement of non-planarity in 2 is probably due to the presence of numerous intermolecular interactions caused by the presence of trifluoroacetate anions on both faces of the porphyrin in addition to the bulky bromine groups at the β-pyrrole positions. In 5, the non-planarity is merely due to the metal coordination at the porphyrin core as pentacoordinated MnIII center with a chloro ligand in the axial position. Hirshfeld surface analysis was performed in order to analyze the various intermolecular interactions present in these porphyrins and the result was discussed.