Cobalt(III)-containing penta-dentate "helmet"-type phthalogens: synthesis, solid-state structures and their thermal and electrochemical characterization

Rasha K Al-Shewiki; Saddam Weheabby; Nell Uhlig; Marcus Korb; Tom Pester; Stefan Zahn; S Grecchi; P R Mussini; Tobias Rüffer; Heinrich Lang

doi:10.1039/d3dt03950a

Cobalt(III)-containing penta-dentate "helmet"-type phthalogens: synthesis, solid-state structures and their thermal and electrochemical characterization

Dalton Trans. 2024 Feb 20;53(8):3836-3854. doi: 10.1039/d3dt03950a.

Authors

Rasha K Al-Shewiki¹, Saddam Weheabby², Nell Uhlig¹, Marcus Korb³, Tom Pester⁴, Stefan Zahn⁵, S Grecchi⁶, P R Mussini⁶, Tobias Rüffer¹, Heinrich Lang⁷

Affiliations

¹ Chemnitz University of Technology, Department of Inorganic Chemistry, Strasse der Nationen 62, 09107, Chemnitz, Germany. tobias.rueffer@chemie.tu-chemnitz.de.
² Chemnitz University of Technology, Measurement and Sensor Technology, 09126 Chemnitz, Germany.
³ University of Western Australia, School of Molecular Sciences, M310, 6009 Perth, WA, Australia.
⁴ Chemnitz University of Technology, Department of Organic Chemistry, Strasse der Nationen 62, 09111, Chemnitz, Germany.
⁵ Leibniz Institute of Surface Engineering (IOM), Permoserstraße 15, 04318 Leipzig, Germany.
⁶ University of Milan, Department of Chemistry, Via Golgi 19, 20133 Milano, Italy.
⁷ Research Center for Materials, Architectures and Integration of Nano-membranes (MAIN) Research Group Organometallic Chemistry, Technische Universität Chemnitz Rosenbergstraße 6, 09126 Chemnitz, Germany.

PMID: 38305694
DOI: 10.1039/d3dt03950a

Abstract

Treatment of unsubstituted and substituted phthalonitrile (1a-d) with appropriate equivalents of sodium methoxide and ammonia afforded the corresponding 1,3-diiminoisoindolines (2a-d), which were converted to cobalt(III)-containing penta-dentate "helmet"-type phthalogens (3a-d) by the reaction with CoCl₂·6H₂O as templating agent in the inert solvent 1,2,4-trichlorobenzene. The identities of 2a-d and 3a-d were established by elemental analysis, infrared spectroscopy (IR), nuclear magnetic resonance (NMR), and electrospray ionization mass spectrometry (ESI-MS). A computational study was performed to determine the most stable tautomeric form of 2a-c in the gas phase. The solid-state structures of 2b and 2c were determined by single crystal X-ray diffraction (SC-XRD) studies to confirm their existence in the stereoisomeric anti-form, which is aligned with quantum chemical computations. SC-XRD studies of 3a and 3b revealed a slightly distorted octahedral geometry around the Co^III ions which are coordinated by five N-donor atoms and one extra co-ligand, resulting in a coordination environment of CoN₅Cl (3a) and CoN₅O (3b), respectively. The thermal stabilities of 2a-d and 3a-d were investigated by thermogravimetric analysis (TGA) in the temperature range of 40-500 °C and 40-800 °C, respectively, revealing that 3a-d were converted to the parent cobalt(II)-containing phthalocyanines (4a-d), which was verified independently by furnace heating experiments. Moreover, the electrochemical behavior of 3a was studied exemplarily for the phthalogens by cyclic voltammetry and square wave voltammetry. This study showed that 4a (CoPc) is formed irreversibly by reducing 3a electrochemically.