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Wheel-Axle Topology Driven Halogen Bonds: Formation of Ladder, 1D and 2D Networks in Hexa-coordinated Sn(IV)Porphyrins


Present study is devoted towards the construction of metalloporphyrin assemblies directed and sustained by halogen bonds (XB) on judiciously selected molecular scaffolds. We choose a series of Sn(axial-L)2–(5,10,15,20-tetraiodoporphyrin) [Sn(L)2-TIPP, where L= halogen/nitro-substituted benzoate moiety] complexes as our building units that resemble a ‘wheel and axle’ topology which aided the construction of different type of molecular assemblies like ladder, 1D and 2D networks. In all the complexes explored herein, the wheel is constructed with Sn(IV)-5,10,15,20-meso-tetrakis(4-iodophenyl)porphyrin [Sn(L)2-TIPP], which is rigid and the two pairs of iodine atoms present at the meso-phenyl position of porphyrin ring can get involved in XB interactions, depending upon the complementary interacting atoms present at the axle. Single crystal X-ray diffraction analysis confirm the occurrence of halogen bonds in crystalline metalloporphyrin assemblies via I•••I, I•••O and I•••π halogen bonds. Most interestingly, these XBs are not only restricted between Wheel•••Axle alone, but also can occur between Wheel•••Wheel and Axle•••Axle. Different types of XB directed molecular associations are observed, for example, ladder type supramolecular associations occur in 1; 2D-network in 2, 3 and 8; interlinked 1D network in 4 and 5; 1D-network in 7. Theoretical studies with Hirshfeld surface analysis show the definite role of XB interactions in the overall stability of the complexes. Electrostatic potential surfaces studies with the aid of Density Functional Theory (DFT) in 2 and 8 show the presence of σ-hole on the cap of iodine atom which further augments the role of XBs in the observed architectures. The structural and theoretical studies presented here showcases that it is necessary to consider an adequate topology such as that of a ‘wheel and axle’ along with complimentary interacting functional groups placed adequately on hexa-coordinated Sn(IV)-porphyrins to realize molecular construction such as Ladder, 1D and 2D networks.

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Publication details

The article was received on 02 Nov 2018, accepted on 29 Dec 2018 and first published on 02 Jan 2019

Article type: Paper
DOI: 10.1039/C8CE01877D
Citation: CrystEngComm, 2019, Accepted Manuscript
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    Wheel-Axle Topology Driven Halogen Bonds: Formation of Ladder, 1D and 2D Networks in Hexa-coordinated Sn(IV)Porphyrins

    J. Rani, G. Kaur, S. S., D. %, R. Yadav, R. Kataria, P. Natarajan, P. Venugopalan, A. Chaudhary and R. Patra, CrystEngComm, 2019, Accepted Manuscript , DOI: 10.1039/C8CE01877D

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