Linear I···I contacts in a platinum(IV)-diiodo porphyrin: Emergent type III halogen–halogen interactions
5 affiliations
- 1Centre for Supramolecular Chemistry Research, Department of Chemistry
- 2University of Cape Town
- 3Department of Chemistry
- 4Department of Chemistry and Polymer Science, Stellenbosch University, Private Bag X1, Matieland, South Africa, 7602
- 5UiT-The Arctic University of Norway
Abstract
This study presents experimental and theoretical evidence for unusual intermolecular I···I interactions between axially coordinated iodide ligands in a Pt(IV) porphyrin. Single-crystal X-ray diffraction reveals that PtI2T[3,5-diOMe]PP, where T[3,5-diOMe]PP is the 5,10,15,20-tetrakis(3,5-dimethoxyphenyl)porphyrinato dianion, crystallises in the uncommon P4/n space group, in contrast to the I4/m space group frequently observed for related metalloporphyrins, and adopts an eclipsed columnar packing arrangement, with co-crystallised dichloromethane (DCM) molecules occupying the space between successive porphyrin layers. The iodide ligands form linear I···I contacts that propagate into a one-dimensional supramolecular network. Comparison with the axial-iodide-free PtT[3,5-diOMe]PP and the related OsI2T[2,4,6-triMe]PP, where T[2,4,6-triMe]PP is the 5,10,15,20-tetrakis(2,4,6-trimethylphenyl)porphyrinato dianion, demonstrates how axial iodide coordination, peripheral substitution, and the local solvent environment influence the resulting crystal packing and macrocyclic conformation. Molecular surface electrostatic potential (MESP), quantum theory of atoms in molecules (QTAIM), natural bond orbital (NBO), and Hirshfeld surface analyses were employed to investigate the nature of the intermolecular contacts. QTAIM analysis identifies the I···I contacts as weak, closed-shell interactions, while NBO analysis reveals a significant donor–acceptor component involving iodide lone pairs and neighbouring Pt–I or Os–I antibonding orbitals. The magnitude and distribution of these interactions depend on the local supramolecular environment, with co-crystallised DCM contributing additional C–H···I contacts and altering the electronic environment of these ligands. Together, these results demonstrate that the I···I interactions cannot be considered in isolation, but instead form part of a broader network of cooperative intermolecular contacts that governs the crystal packing of the Pt(IV) porphyrin.
Related
- Synthesis, crystal structure, Hirshfeld surface analysis and halogen-involving interactions in a bromo/chloro-substituted Schiff base 1-(3-bromo-4,5-dimethoxyphenyl)-N-(2,4-dichlorophenyl)methanimine
- Reducing photosensitizer aggregation via cyclodextrin-adamantane porphyrin host-guest interactions for enhanced photodynamic therapy.
- Systematic Evaluation of Halogen Substitution in ortho-Benzoxy Phenylboronic Acid Catalysts for Amidation Reactions
- EXAFS probing of nonequilibrium solvation dynamics of nascent halogen radicals
- 本科生综合实验：基于卤键有机框架材料的分散固相萃取方法构建及在溴代阻燃剂分析中的应用 A comprehensive undergraduate experiment： development of a dispersive solid-phase extraction method based on halogen-bonded organic frameworks and its application to the analysis of brominated flame retardants
BibTeX
@misc{theunissen2026linear,
title = {{Linear I···I contacts in a platinum(IV)-diiodo porphyrin: Emergent type III halogen–halogen interactions}},
author = {Tristan K. Theunissen and Gerhard A. Venter and Catharine Esterhuysen and Abhik Ghosh and Susan A. Bourne},
howpublished = {ChemRxiv},
year = {2026},
month = sep,
doi = {10.26434/chemrxiv.15009151/v1},
url = {https://chemrxiv.org/doi/full/10.26434/chemrxiv.15009151/v1},
note = {CC BY},
}
RIS
TY - UNPB
TI - Linear I···I contacts in a platinum(IV)-diiodo porphyrin: Emergent type III halogen–halogen interactions
AU - Tristan K. Theunissen
AU - Gerhard A. Venter
AU - Catharine Esterhuysen
AU - Abhik Ghosh
AU - Susan A. Bourne
PY - 2026
DA - 2026/09/21
PB - ChemRxiv
DO - 10.26434/chemrxiv.15009151/v1
UR - https://chemrxiv.org/doi/full/10.26434/chemrxiv.15009151/v1
AB - This study presents experimental and theoretical evidence for unusual intermolecular I···I interactions between axially coordinated iodide ligands in a Pt(IV) porphyrin. Single-crystal X-ray diffraction reveals that PtI2T[3,5-diOMe]PP, where T[3,5-diOMe]PP is the 5,10,15,20-tetrakis(3,5-dimethoxyphenyl)porphyrinato dianion, crystallises in the uncommon P4/n space group, in contrast to the I4/m space group frequently observed for related metalloporphyrins, and adopts an eclipsed columnar packing arrangement, with co-crystallised dichloromethane (DCM) molecules occupying the space between successive porphyrin layers. The iodide ligands form linear I···I contacts that propagate into a one-dimensional supramolecular network. Comparison with the axial-iodide-free PtT[3,5-diOMe]PP and the related OsI2T[2,4,6-triMe]PP, where T[2,4,6-triMe]PP is the 5,10,15,20-tetrakis(2,4,6-trimethylphenyl)porphyrinato dianion, demonstrates how axial iodide coordination, peripheral substitution, and the local solvent environment influence the resulting crystal packing and macrocyclic conformation. Molecular surface electrostatic potential (MESP), quantum theory of atoms in molecules (QTAIM), natural bond orbital (NBO), and Hirshfeld surface analyses were employed to investigate the nature of the intermolecular contacts. QTAIM analysis identifies the I···I contacts as weak, closed-shell interactions, while NBO analysis reveals a significant donor–acceptor component involving iodide lone pairs and neighbouring Pt–I or Os–I antibonding orbitals. The magnitude and distribution of these interactions depend on the local supramolecular environment, with co-crystallised DCM contributing additional C–H···I contacts and altering the electronic environment of these ligands. Together, these results demonstrate that the I···I interactions cannot be considered in isolation, but instead form part of a broader network of cooperative intermolecular contacts that governs the crystal packing of the Pt(IV) porphyrin.
ER -