ISSN print edition: 0366-6352 ISSN electronic edition: 1336-9075 Registr. No.: MK SR 9/7 Published monthly

Mn(III)-tris(benzoylacetonate) complex exhibiting a static rotational disorder: synthesis, crystal structure, magnetic properties, and DFT computations

Abdenour Guerraoui, Meriem Goudjil, Mauro Perfetti, Marrigje Marianne Conradie, Jeanet Conradie, Hamza Athmani, Samuele Ciattini, and Amel Djedouani

Laboratory of Structures, Properties and Interatomic Interactions LASPI 2A, Faculty of Sciences and Technology, Abbes Laghrour University, Khenchela, Algeria

E-mail: abdenourguerraoui@gmail.com

Received: 9 August 2025  Accepted: 19 November 2025

Abstract:

The mixture of manganese acetates and the asymmetrical benzoylacetone ligand (bzacH) crystallized into a monomeric Mn(III)-tris(benzoylacetonato) complex, [Mn(bzac)₃]. The crystal structure of [Mn(bzac)₃] revealed a static rotational disorder, where half [Mn(bzac)₃] molecule adopts the Λ configuration and the other is in the Δ configuration. Both molecules are mer-isomers, exhibiting Jahn-Teller elongation along two opposing Mn–O–CMe bonds (mer-Me-Me). [Mn(bzac)₃] was further characterized by IR spectroscopy, thermogravimetric analysis (TGA/DTA), magnetic susceptibility measurements, UV-Vis spectroscopy, Hirshfeld surface analysis and Density functional theory (DFT) calculations. The Hirshfeld surface analysis, complemented by 2D fingerprint plots, confirms the presence of significant intermolecular interactions, including H···H, H···O, H···C hydrogen bonding, and C—H···π stacking interactions. Magnetic measurements reveal a high-spin Mn(III) center with an S = 2 state with relevant Zero-Field Splitting (D = -4.50 cm⁻¹, g = 2.00) and slow magnetization relaxation at low temperatures. DFT calculations support the experimentally observed high-spin state of [Mn(bzac)₃] and provide insights into its electronic structure. HOMO analysis suggests that the Jahn-Teller elongation along the axial Mn–O bonds arises from electrostatic interactions between the Mn 3d_z² orbital and the p_z orbitals of the axial oxygen atoms, leading to the energetic stabilization of the HOMO relative to the d_x²−y² LUMO. DFT also identifies four possible Jahn-Teller elongation isomers: one facial (fac) and three meridional (mer) forms. Among these, the experimentally observed mer-Me-Me isomer becomes increasingly favorable at elevated temperatures.

Keywords: Benzoylacetone; Manganese(III) complex; Enantiomers; Hirshfeld surface analysis; Paramagnetic complex

Full paper is available at www.springerlink.com.

DOI: 10.1007/s11696-025-04539-x

Chemical Papers 80 (3) 2661–2679 (2026)