March 3, 2026SHILAP Revista de lepidopterología0 citationsOpen Access

Eugenol-Derived Bipyridine Ligand Scaffolds: Design, Metal Coordination, and Catalytic Applications in Cyclic Carbonate Synthesis

MHMohsin HassanUniversity of Kashmir DDDonald J. DarensbourgMitchell Institute GBGulzar A. BhatUniversity of Kashmir

Key Points

Cyclic carbonate synthesis achieved high selectivity using eugenol-derived ligand as an organocatalyst, showing promising results.
The synthesized ligand engaged in metalation with manganese and rhenium complexes, forming stable conjugated structures.
Electrochemical analyses illustrated distinct reduction and oxidation behaviors characterizing the metal complexes, informing on their stability.
This approach may enable further development of efficient catalysts using bio-derived compounds for sustainable applications.

Abstract

This work reports the synthesis of bis-(4-allyl-2-methoxyphenyl) 2,2'-bipyridine-5,5'-dicarboxylate (bpyEu) (1) derived from the conjugation of 2,2'-5,5'-dicarboxylic acid with the natural product eugenol. This hybrid bis-eugenol ligand integrates π-conjugated bipyridine with a phenolic ether moiety. After successful multigram synthesis of this bipyridine ligand 1, its metalation was explored by reacting with M-(CO)5X, where M = Mn, Re and X = Br, Cl, resulting in the formation of M-(bpyEu)-(CO)3X, where M = Mn, X = Br (2); M = Re, X = Cl (3). The hybrid ligand (1) and its transition metal complexes 2 and 3 were thoroughly characterized by different spectroscopic techniques, such as NMR and Fourier transform infrared (FTIR) spectroscopy, which confirmed their formation, and their molecular structures were established using single-crystal XRD in the solid state and mass spectrometry in solution. The electrochemical behaviors of 2 and 3 were further investigated by cyclic voltammetry. Compound 2 exhibited reversible reductions at -0.828 V and -1.493 V with an irreversible oxidation at +1.44 V, whereas complex 3 displayed a reversible reduction at -0.66 V and -1.08 V along with an irreversible metal-centered oxidation at +1.69 V. Further, we used bis-eugenol-based ligand 1 as an organocatalyst for the cycloaddition of CO2 with epoxides, which showed excellent selectivity for cyclic carbonate synthesis without the need for a cocatalyst. The catalytic activities of complexes 2 and 3 were also evaluated for cyclic carbonate synthesis, which revealed that these metal complexes lacked the catalytic ability for this transformation.

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