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Nature of Fluorine Interactions in ‘Wheel and Axle’ Topology Based Hexa-Coordinated Sn(IV)-Porphyrins: An Experimental and Theoretical Analysis

Abstract

This study targets the construction of metalloporphyrin assemblies directed by fluorine-centered non-covalent interactions that can conveniently operate on a metallated tetrapyridylporphyrin system which topologically resembles a Wheel-Axle duo. We chose a series of Sn(axial-L)2–(5,10,15,20-tetrapyridylporphyrin) [Sn(L)2-TPyP, where L= fluorine-substituted benzoate moiety] complexes as our building units, which has only one fluorine atom on the benzoate moiety (compound 1 and 2) but progressively increased to 2 (compound 3) and to 5 (compound 4). This stepwise augmentation also showed concomitant increase in fluorine-based intermolecular interactions. Four complexes with varying F:H ratio of 1:4 to 5:0 at the axle part of the molecule were structurally analyzed by single-crystal X-ray diffraction. Fluorine-centered intermolecular interactions have been investigated and found to correlate with the number of fluorine atoms present at the axial benzoato-ligand of the wheel-axle duo. The augmentation in the number of fluorine-centered interactions was theoretically supported by Hirshfeld surface analysis showing a steep increase from 11% (1/2) to 20% (3) to 39% (4) as a function of the degree of fluorine-substitution. However, Electrostatic Potential Surface (ESP) analysis clearly negates the formation of sigma-hole at fluorine atoms and thus vitiates their role as XB donors in these complexes. The occurrence of such short-contacts as an artifact of the ‘Gulliver effect’ should not be ruled out in fluorine based crystal engineering attempts.

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Supplementary files

Article information


Submitted
04 Mar 2020
Accepted
25 Jun 2020
First published
26 Jun 2020

CrystEngComm, 2020, Accepted Manuscript
Article type
Paper

Nature of Fluorine Interactions in ‘Wheel and Axle’ Topology Based Hexa-Coordinated Sn(IV)-Porphyrins: An Experimental and Theoretical Analysis

J. Rani, A. Arora, J. I. Ahmed, D. Adhikari, P. Natarajan, P. Venugopalan and R. Patra, CrystEngComm, 2020, Accepted Manuscript , DOI: 10.1039/D0CE00333F

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