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Catalysis enabled synthesis, structures, and reactivities of fluorinated S8-corona[n]arenes (n = 8–12)† † Electronic supplementary information (ESI) available: Full experimental and characterisation data. Primary kinetic and guest binding data (Excel format). CCDC 2175101–2175106. For ESI and crystallographic data in CIF or other electronic format see DOI: https://doi.org/10.1039/d2sc05348a

ABSTRACT: Previously inaccessible large S8-corona[n]arene macrocycles (n = 8–12) with alternating aryl and 1,4-C6F4 subunits are easily prepared on up to gram scales, without the need for chromatography (up to 45% yield, 10 different examples) through new high acceleration SNAr substitution protocols (catalytic NR4F in pyridine, R = H, Me, Bu). Macrocycle size and functionality are tunable by precursor and catalyst selection. Equivalent simple NR4F catalysis allows facile late-stage SNAr difunctionalisation of the ring C6F4 units with thiols (8 derivatives, typically 95+% yields) providing two-step access to highly functionalised fluoromacrocycle libraries. Macrocycle host binding supports fluoroaryl catalytic activation through contact ion pair binding of NR4F and solvent inclusion. In the solid-state, solvent inclusion also intimately controls macrocycle conformation and fluorine–fluorine interactions leading to spontaneous self-assembly into infinite columns with honeycomb-like lattices. NR4F salts simultaneously catalyse and template the reaction of dithiols with C6F6 to generate the first fluorinated corona[n]arenes. Simple SNAr functionalisation of the fluoraryl units easily afford diverse libraries of macrocyclic building blocks.

SUBMITTER: Turley A

PROVIDER: S-EPMC9769089 | biostudies-literature | 2022 Nov

REPOSITORIES: biostudies-literature

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Project description:Mononuclear non-heme iron complexes that serve as structural and functional mimics of the thiol dioxygenases (TDOs), cysteine dioxygenase (CDO) and cysteamine dioxygenase (ADO), have been prepared and characterized with crystallographic, spectroscopic, kinetic, and computational methods. The high-spin Fe(II) complexes feature the facially coordinating tris(4,5-diphenyl-1-methylimidazol-2-yl)phosphine (Ph2TIP) ligand that replicates the three histidine (3His) triad of the TDO active sites. Further coordination with bidentate l-cysteine ethyl ester (CysOEt) or cysteamine (CysAm) anions yielded five-coordinate (5C) complexes that resemble the substrate-bound forms of CDO and ADO, respectively. Detailed electronic-structure descriptions of the [Fe(Ph2TIP)(LS,N)]BPh4 complexes, where LS,N = CysOEt (1) or CysAm (2), were generated through a combination of spectroscopic techniques [electronic absorption, magnetic circular dichroism (MCD)] and density functional theory (DFT). Complexes 1 and 2 decompose in the presence of O2 to yield the corresponding sulfinic acid (RSO2H) products, thereby emulating the reactivity of the TDO enzymes and related complexes. Rate constants and activation parameters for the dioxygenation reactions were measured and interpreted with the aid of DFT calculations for O2-bound intermediates. Treatment of the TDO models with nitric oxide (NO)-a well-established surrogate of O2-led to a mixture of high-spin and low-spin {FeNO}7 species at low temperature (-70 °C), as indicated by electron paramagnetic resonance (EPR) spectroscopy. At room temperature, these Fe/NO adducts convert to a common species with EPR and infrared (IR) features typical of cationic dinitrosyl iron complexes (DNICs). To complement these results, parallel spectroscopic, computational, and O2/NO reactivity studies were carried out using previously reported TDO models that feature an anionic hydrotris(3-phenyl-5-methyl-pyrazolyl)borate (Ph,MeTp-) ligand. Though the O2 reactivities of the Ph2TIP- and Ph,MeTp-based complexes are quite similar, the supporting ligand perturbs the energies of Fe 3d-based molecular orbitals and modulates Fe-S bond covalency, suggesting possible rationales for the presence of neutral 3His coordination in CDO and ADO.

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