Fluorinated Porphyrinic Crystalline Solids: Structural Elucidation and Study of Intermolecular Interactions

Crystal engineering is an emerging area of research in material, biological, and pharmaceutical chemistry that involves synthesis of new materials, analysis of its structure including intermolecular interactions using X‐ray crystallography as well as computational methods. It has been shown that the intermolecular interactions involving organic fluorine such as C−F∙∙∙H, F∙∙∙F, and C−F∙∙∙π play an important role in stabilizing the supramolecular assemblies, especially in the absence of strong intermolecular forces. Recently, non‐covalent interactions involving conjugated aromatic system such as porphyrins have been studied intensively. The synthetic porphyrins are of widespread attention because of their close resemblance to naturally occurring tetrapyrrolic pigments and they find various materials and biological applications. In this book chapter, we disclose our recent findings on detailed crystal structure analysis of a few series of fluorinated porphyrins using single‐crystal XRD as well as computational Hirshfeld surface analysis to understand the role of close contacts involving fluorine in the molecular crystal packing

Pentafluorophenyl dipyrrin as probe for transition metal ion detection and bioremediation in Bacillus subtilis and Bacillus cereus

Recognition of transition metal ions and bioaccumulation in B. subtilis and B. cereus were examined using pentafluorophenyl dipyrrin probe.</p

Mono- and di-(2,3,5,6-tetrafluoro-4-N,N-dimethylaminophenyl) <i>meso</i>-tetraarylporphyrins: Synthesis, spectral, structural and electrochemical studies

A new series of mono-/di-aminated meso-tetraarylporphyrins has been synthesized and characterized by conventional spectroscopic methods. Crystal structure analysis shows that interactions involving halogens are the major contributors, and the relative contributions are 56% and 53% respectively for MB2c and MB3c. All the compounds were electrochemically analyzed under different reaction conditions and showed a positive shift in the reduction and oxidation potentials. The HOMO–LUMO energy gap was altered with respect to the nature of the supporting electrolyte and reference electrodes used. The linear behavior of Randles-Sevcik plots indicate that the redox processes are diffusion controlled; the first reduction/oxidation is a reversible one-electron step whereas the second reduction/oxidation is a quasi-reversible one-electron process. Results also reveal that the mono-aminated porphyrins are more electron deficient than non-aminated and di-aminated porphyrins. </jats:p

A “turn-on-and-off” pH sensitive BODIPY fluorescent probe for imaging <i>E. coli</i> cells

Highly selective fluorescent BODIPY probes towards H+ ions displayed good photostability and reversibility and the utility of acid sensitive behavior to visualize extreme acidity in E. coli cells is also demonstrated.</p

Semiconductive properties of zinc(II)-porphyrinic coordination arrays

Two coordination polymers, 1 and 2 were developed utilizing the favorable hexacoordinated zinc(II) center in porphyrins. Single crystal X-ray structure analysis revealed that 1 forms one dimensional array whereas 2 display three dimensional network structures. Scanning tunnelling microscopic studies have shown that compounds 1 and 2 can tunnel the electric current through the crystal lattice indicating the conducting behavior of these solid crystals. The self-assembled solid crystal 2 has shown uniform conductance whereas 1 does not. The thermal stability of these crystals were determined by TGA analysis and found to be stable up to a higher temperature of 400°C. A temperature dependent current–voltage analysis were also performed and the results indicate that the conductivity of crystals 1 and 2increases with increase in temperature. It is found that the temperature coefficient of resistance ([Formula: see text] at 100°C for 1 and 2 as -0.009 and 0.017 K[Formula: see text]. </jats:p

Influence of steric hindrance on the solvent-dependent absorption spectral behavior of highly brominated free base porphyrin and its <font>Zn</font>(II) complex

Electronic absorption spectra of highly brominated free base porphyrin, 2,3,7,8,12,13,17,18-octabromo-tetrakis(2′,6′-dibromo-3′,5′-dimethoxyphenyl)porphyrin, H 2 T (3′,5′-DMP) PBr 16 and its Zn (II) complex were examined in various solvents. These derivatives exhibit red-shifted absorption spectral features in polar solvents relative to that observed in less polar or nonpolar solvents. The extent of red shifts observed in highly brominated porphyrins is less than those reported for the corresponding 2,3,7,8,12,13,17,18-octabromo-5,10,15,20-tetraphenylporphyrin, H 2 TPPBr 8 and its Zn (II) complex. The crystal structure of the H 2T(3′,5′-DMP) PBr 16 showed saddle-shaped geometry with steric hindrance of the bromo groups on the opposite phenyl rings which provide limited open access to the core. The decreased red shift of the absorption spectral bands of MT (3′,5′-DMP) PBr 16 ( M = 2 H , Zn (II)) derivatives when compared to unhindered MTPPBr 8 is possibly due to the steric hindrance offered by the ortho-bromo groups rather than the electronic effects of the porphyrin π-system. </jats:p

Protonation and axial ligation intervened fluorescence turn-off sensing of picric acid in freebase and tin(<scp>iv</scp>) porphyrins

Protonation and axial ligation: selective sensing of picric acid using freebase and tin(iv) meso-tetraarylporphyrins occurs through protonation and axial ligation which is evident from UV-visible, fluorescence, 1H NMR titrations and X-ray crystallography.</p