New heteroleptic l-argininato copper(II) complex with bromide and N, N’– heterocyclic ligands – synthesis, supramolecular, spectroscopic, magnetic and theoretical investigations

• Published in: Journal of molecular structure 2024-07, Vol.1308, p.138094, Article 138094
• Main Authors: Walkowiak, Zuzanna, Gągor, Anna, Soliman, Saied M., Jerzykiewicz, Maria, Sarewicz, Marcin, Fitta, Magdalena, Pełka, Robert, Wojciechowska, Agnieszka
• Format: Article
• Language: English
• Subjects: Antiferromagnetic; Bromide; Copper(II); Hirshfeld; L−arginine; Spectroscopies; Structure
• ISSN: 0022-2860
• DOI: 10.1016/j.molstruc.2024.138094

•The [CuBr(l−Arg)(bpy)]+ units exhibit a ribbon−like organization with metal centers located at the corners of triangles.•The molecular packing is controlled by H∙∙∙H and Br∙∙∙H interactions.•The EPR data from Q-band solid state spectra indicate local octahedral elongated structure.•In aqueous solution, [Cu(l−Arg)(bpy)]2+ species partially transform into [Cu(bpy)]2+ entities.•The weak antiferromagnetic coupling between magnetic moments of the complex was found. A new heteroleptic [CuBr(l−Arg)(bpy)]Br·2H2O (1) (l−Arg=l−Arginine, bpy=2,2’−bipyridine) complex has been synthesized and its molecular and supramolecular structure aspects have been discussed based on the X−ray single crystal structure and Hirshfeld analyses. In addition, the properties of complex 1 have been elucidated using different spectroscopic methods (FT−IR / FIR, Raman, NIR−Vis−UV, Q− / X− band EPR) and magnetic measurements. In this complex, the bromide anion occupies the apex of a slightly distorted square pyramid (τ = 0.12). The [CuBr(l−Arg)(bpy)]+ complex units exhibit a ribbon−like organization, with Cu(II) metal centers located at the corners of triangles where the shortest Cu∙∙∙Cu distance is 5.579 Å. The aromatic moieties of bpy are aligned nearly parallel leading to π···π interactions. Both, non−bonded and coordinated, Br− ions act as hydrogen−bond acceptors for guanidinium groups. Hirshfeld analysis indicated the importance of the Br∙∙∙H (17.9 − 18.4 %), O∙∙∙H (14.9−15.2 %), and H∙∙∙H (42.3−43.1 %) interactions in the molecular packing of the studied complex. Atoms in molecules (AIM) calculations indicated mainly the closed shell character for the Cu−N, Cu−O and Cu−Br coordination interactions. The G value calculated using the Q−band EPR spectra parameters g|| = 2.235 and g⊥= 2.05 is 4.7, what indicating negligible coupling and that local tetragonal axes are aligned parallel. A negative value of Weiss temperature θCW = -0.32 K indicates the presence of weak antiferromagnetic coupling between the neighboring Cu(II) ions mediated through hydrogen bonds and π-π stacking of aromatic moieties of bpy. The value of gav= 2.113 obtained from Q−band EPR spectra is consistent with that corresponding to the Curie constant (C = 0.4138 emu K mol−1), i.e.g = 2.101, and that obtained from the best fitting to the Brillouin function: g = 2.139. [Display omitted]