Electrochemical, Photophysical, Morphological and DFT Study of Polymorphic Sn(IV)‐Porphyrins Containing Fluorinated Axial Ligand

Abstract

In this study, we report the polymorphism of six coordinated Sn(IV)‐ tetrabromophenyl porphyrins axially armed with fluorine‐substituted phenolate ligands (structural formula [Sn(TBrPP)2+(A−)2], where A is the axial ligand=3,5‐difluoro phenol, compound 1). One form stabilizes in triclinic system (namely, 1α), and the other stabilizes in monoclinic system (namely, 1β). The two 1α and 1β polymorphs display distinct photophysical and morphological properties in the solid state. X‐ray diffraction study reveals that these polymorphs 1α and 1β significantly differ in their supramolecular architecture, different axial phenolate conformations, and noncovalent interactions, which are responsible for their distinct solid‐state properties. The crystal packing of these polymorphs dominates by intermolecular C−H⋅⋅⋅F, C−H⋅⋅⋅π and C−Br⋅⋅⋅F interhalogen interactions. Furthermore, the solid‐state emission spectra of 1α showed red‐shifted emission bands with respect to 1β, in addition the redox behavior of 1α is slightly different in comparison to 1β. Complementary theoretical studies with Hirshfeld surface analysis show the definite role of Br⋅⋅⋅F interhalogen interactions in the overall stability. Mapping the electrostatic potential isosurfaces with the aid of density functional theory in compound 1 clearly shows the presence of σ‐hole, a requisite feature to show halogen interactions in the crystalline state. In addition, lattice energy and single point energy calculation shows that 1α was found to be energetically more favorable and thermodynamically more stable compare to 1β.

Dielectronic properties and photocatalytic activities of two novel cobalt(II) meso-tetraphenylporphyrin-based coordination complexes

“…The interaction of metalloporphyrins with donor molecules via axial coordination can strongly influence either the photophysical properties and the efficiency of energy or the electron transfer processes [8]. Over the last few decades, many crystalline structures of porphyrins or metalloporphyrins whose optical properties and crystal packing are governed by axial ligands coordination modes have been reported [9]. Among the M(II)-porphyrins, cobalt(II) porphyrins are the most studied compounds, since they are more sensitive to light irradiation and can change their oxidation state [10].…”

Impact of Electron-Withdrawing Effect on Sigma Hole Via Bromine-Based Interactions in Zn-5,10,15,20-tetra(4-bromo-2,6-difluoro Phenyl) Porphyrin

“…Row et al reported a database study which highlights the role of C-halogen···π interactions that aids the halogenated ligands to bind effectively to the target nucleic acids . Goldberg and his colleagues have documented numerous supramolecular structures using molecular building blocks derived from tetra­(iodophenyl) porphyrin (TIPP) and its derivatives. − Patra et al demonstrated the influence of an axial linker toward the size of σ-holes on halogen atoms for hexacoordinated tin tetra­(iodophenyl) porphyrin scaffolds. , Nandi and Goldberg reported the occurrence of cooperative halogen bonding between the multi-porphyrin coordination assemblies …”

“…30−32 Patra et al demonstrated the influence of an axial linker toward the size of σ-holes on halogen atoms for hexacoordinated tin tetra(iodophenyl) porphyrin scaffolds. 33,34 Nandi and Goldberg reported the occurrence of cooperative halogen bonding between the multi-porphyrin coordination assemblies. 35 Spilfogel and colleagues conducted a database study of bromine-based halogen bonding interactions between porphyrins.…”

Homo- and hetero-halogen interaction based molecular associations in wheel–axle topology derived Sn(iv) porphyrin complexes: an experimental and theoretical analysis

“…Recently we have also reported the effect of hetero-halogen interactions on crystal packing and solid-state properties like polymorphism. 21 Compounding difficulties in understanding the nature of X⋯X (hetero-halogen) interactions also arise due to a significant range in the electronegativity (F > Cl > Br > I) and polarizability (I > Br > Cl > F) of different halogens. [11][12][13] Thus, depending on the circumstances, a halogen acts as either an electropositive or an electronegative entity, or in some cases with no particular electrostatic character.…”