A novel class of zinc(II)-based metal complexes, i.e., [Zn 2 (acdp)(μ-Cl)]•2H 2 O (1), [Zn 2 (acdp)(μ-NO 3 )]•2H 2 O (2), and [Zn 2 (acdp)(μ-O 2 CCF 3 )]•2H 2 O (3) (Cl − = chloride; NO 3 − = nitrate; CF 3 CO 2 − = trifluoroacetate) of anthracene-affixed multifunctional organic assembly, H 3 acdp (H 3 acdp = N,N′-bis-[anthracene-2-ylmethyl]-N,N′-bis[carboxymethyl]-1,3-diaminopropan-2-ol), have emerged as promising antibacterial and antibiofilm agents in the domain of medicinal chemistry. Accordingly, complexes 1−3 were synthesized by utilizing H 3 acdp in combination with ZnCl 2 , Zn(NO 3 ) 2 •6H 2 O, and Zn(CF 3 CO 2 ) 2 •H 2 O respectively, in the presence of NaOH at ambient temperature.The complexation between H 3 acdp and Zn 2+ was delineated by a combined approach of spectrophotometric and spectrofluorometric titration studies. The stoichiometry of acdp 3− /Zn 2+ in all three complexes is observed to be 1:2, as confirmed by spectrophotometric/spectrofluorometric titration data. Elemental analysis (C, H, N, Zn), molar conductance, FTIR, UV−vis, and thermoanalytical (TGA/DTA) data were effectively used to characterize these complexes. Besides, the structures of 1−3 were established by density functional theory (DFT) calculation using B3LYP/6-311G, specifying a self-assembled compact geometry with average Zn•••Zn separation of 3.4629 Å. All three zinc complexes exhibited significantly high antibacterial and antibiofilm activity against methicillin-resistant Staphylococcus aureus (MRSA BAA1717). However, complex 1 showed a more recognizable activity than 2 and 3, with minimum inhibitory concentration (MIC) values of 200, 350, and 450 μg/mL, respectively. The antimicrobial activity was tested by employing the minimum inhibitory concentration (MIC) and time-kill assay. The crystal violet (CV) assay and microscopic study were performed to examine the antibiofilm activity. As observed, complexes 1−3 had an effect on the production of extracellular polymeric substance (EPS), biofilm cell-viability, and other virulence factors such as staphyloxanthin and hemolysin production, autoaggregation ability, and microbial cell-surface hydrophobicity. Reactive oxygen species (ROS) generated due to inhibition of staphyloxanthin production in response to 1−3 were also analyzed. Moreover, complexes 1−3 showed an ability to damage the bacterial cell membrane due to accumulation of ROS resulting in DNA leakage. In addition, complexes 1−3 displayed a synergistic/additive activity with a commercially available antibiotic drug, vancomycin, with enhanced antibacterial activity. On the whole, our investigation disclosed that complex 1 could be a promising drug lead and attract much attention to medicinal chemists compared to 2 and 3 from therapeutic aspects.

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Crystallization of ionic liquids (ILs) is of great interest for determining the crystal structure and molecular interactions. Hydrogen bonding is an important noncovalent interaction, which is related to the properties of ILs. In this context, we have prepared 1,1,3,3-tetramethylguanidine (TMG)-based ILs with different benzoic acid derivatives as anions and the crystal structures of these ILs were determined at low temperature (173(2) K) to understand the interactions and their network formation. Using Hirshfeld surface analysis, the intermolecular interactions in the crystal packing of ILs were analyzed and quantified. Density functional theory (DFT) calculations were carried out to ascribe the thermodynamic properties of these ILs. The molecular geometry of the guanidinium ionic liquids was optimized, and the electronic properties and HOMO and LUMO energies were calculated using DFT at the B3LYP/6-311G++(d,p) level. The characterization of the ILs was done by TGA, DSC, NMR, and IR.

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