Department of Chemistry
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Item Asymmetrically β-Substituted Porphyrins and Chlorins: Synthesis, Spectroscopic, and Electrochemical Redox Properties(IOP, 2015) Grover, NitikaAsymmetrically β-substituted chlorins, viz. 2,3-bis(dicyanomethyl)-meso-tetraphenylchlorin (1), diethoxycarbonylcyclopropano-meso-tetraphenylchlorin (2) and 2-ethylacetoacetanato-meso-tetraphenylporphyrin (3), and their metal (Ni(II), Cu(II) and Zn(II)) complexes have been synthesized and characterized by various spectroscopic techniques. Cyclic voltammetric (CV) studies were carried out for these porphyriniods in CH2Cl2 containing TBAPF6 as supporting electrolyte. The first ring redox potentials of 1, 2 and their metal complexes are anodically shifted (0.58 - 0.30 V) as compared to meso-tetraphenylchlorin (H2TPC) due to electron withdrawing nature of malononitrile and diethyl malonate substituents. Notably, Ni(II) complex of 3 exhibited metal centered oxidation (NiII/NiIII) due to extended conjugation and electronic nature of β-subtituent.Item β-Heptasubstituted Porphyrins: Synthesis, Structural, Spectral, and Electrochemical Properties(Wiley, 2018-06) Grover, NitikaA new series of β-heptasubstituted porphyrins MTPP(NO2)(Me)6 (M = 2H, CoII, NiII, CuII, and ZnII) was synthesized and characterized by various spectroscopic techniques. The single-crystal X-ray structure analysis of CoTPP(NO2)(Me)6 revealed the significant saddle distortion of the macrocyclic core from the porphyrin mean plane (ΔCβ = 0.928 Å). These porphyrins exhibit significant redshifted electronic spectral features (Δλmax = 40–62 nm) as compared with MTPP due to the combined effect of the nonplanar conformation of the macrocyclic core and mixed β-substituents. H2TPP(NO2)(Me)6 has shown a high dipole moment (7.12 D) as compared with H2TPP (0.052 D) due to cross-polarized push–pull substituents. The redox tunability was achieved by appending the electron-donating methyl and electron-withdrawing NO2 group at the β-positions of the porphyrin skeleton.Item Synthesis and Structure of meso-Substituted Dibenzihomoporphyrins(Wiley, 2020-09) Grover, NitikaBench-stable meso-substituted di(p/m-benzi)homoporphyrins were synthesized through acid-catalyzed condensation of dipyrrole derivatives with aryl aldehydes. The insertion of a 1,1,2,2-tetraphenylethene (TPE) or but-2-ene-2,3-diyldibenzene unit in the porphyrin framework results in the formation of dibenzihomoporphyrins, merging the features of hydrocarbons and porphyrins. Single crystal X-ray analyses established the non-planar structure of these molecules, with the phenylene rings out of the mean plane, as defined by the dipyrromethene moiety and the two meso-carbon atoms. Spectroscopic and structural investigations show that the macrocycles exhibit characteristics of both TPE or but-2-ene-2,3-diyldibenzene and dipyrromethene units indicating the non-aromatic characteristics of the compounds synthesized. Additionally, the dibenzihomoporphyrins were found to generate singlet oxygen, potentially allowing their use as photosensitizers.Item Nonplanar porphyrins: synthesis, properties, and unique functionalities(RSC, 2022) Grover, NitikaPorphyrins are variously substituted tetrapyrrolic macrocycles, with wide-ranging biological and chemical applications derived from metal chelation in the core and the 18π aromatic surface. Under suitable conditions, the porphyrin framework can deform significantly from regular planar shape, owing to steric overload on the porphyrin periphery or steric repulsion in the core, among other structure modulation strategies. Adopting this nonplanar porphyrin architecture allows guest molecules to interact directly with an exposed core, with guest-responsive and photoactive electronic states of the porphyrin allowing energy, information, atom and electron transfer within and between these species. This functionality can be incorporated and tuned by decoration of functional groups and electronic modifications, with individual deformation profiles adapted to specific key sensing and catalysis applications. Nonplanar porphyrins are assisting breakthroughs in molecular recognition, organo- and photoredox catalysis; simultaneously bio-inspired and distinctly synthetic, these molecules offer a new dimension in shape-responsive host–guest chemistry. In this review, we have summarized the synthetic methods and design aspects of nonplanar porphyrin formation, key properties, structure and functionality of the nonplanar aromatic framework, and the scope and utility of this emerging class towards outstanding scientific, industrial and environmental issues.