Molecular self-assembly of 1D infinite polyiodide helices in a phenanthrolinium salt.

Tomasz Poręba,Marcin Świątkowski,Rafał Kruszyński

doi:10.1039/d0dt04042h

Tomasz Poręba, Marcin Świątkowski + Show 1 more

Open Access

https://doi.org/10.1039/d0dt04042h

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Abstract

A new linear polymeric polyiodide, catena-poly[tris(1,10-phenanthrolin-1-ium)tris(1,10-phenanthroline)heptaiodide], was prepared by one-step synthesis. Its formation is driven by hydrogen-bond assisted supramolecular assembly in the presence of chromium(iii) acetate. Its structure has been characterized by the means of single-crystal X-ray diffraction. To date, this is only one of the few examples of organized linear infinite polyiodides with a known structure. The interplay between the interactions within the hypervalent iodine chain and its supramolecular environment is elucidated. The electrical, thermal, and spectroscopic properties of the studied compound were investigated and associated with the structural features. The infinite character of the polyiodide chain and its similarity to the blue starch-iodine complex has been additionally confirmed by Raman spectroscopy. Despite the apparent structural and spectroscopic similarities with the previously reported 1D polymeric polyiodide, its physical properties, i.e. electrical conductivity and thermal stability, differ significantly. This can be rationalized by the differences in the orbital overlap within the iodine chain, as well as the distinct interactions with the cation.

Highlights

IntroductionAppropriate cation tailoring and reaction conditions can lead to the formation of extended polyiodide systems
Polyiodides are inorganic anions which can be often described with a general formula In−2m+n, where n indicates the number of iodide anions and m the number of iodine molecules
The synthesized compound consists of ordered linear polymeric Inδ− chains and stacks of phenanthrolinium cations and phenanthroline molecules

Summary

Introduction

Appropriate cation tailoring and reaction conditions can lead to the formation of extended polyiodide systems. They have been registered as weakly interacting I3−⋯I3− (intermolecular distance >4.0 Å),[26] linear chains interconnected with I3− perpendicular to the propagation axis,[27,28] or a pure linear chain with alternating I–I distances in (Me4Sb)3I8.29 In the latter example, doubts about its structure have been raised on the basis of theoretical calculations.[30,31,32] Recently, an infinite linear polyiodide chain has been registered in a pyrroloperylene–iodine compound ( prpi).[33] The formation of this structure was achieved by the confinement of polyiodide units within channels along the stacks of the planar cations. The presented data are compared to a very similar reported structure of the infinite polyiodide chain, and are related to the elusive structure of a starch–iodine system.[52,53]

Synthesis procedures

Results and discussion

Conclusions