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Half-sandwich organometallic rhodium and iridium complexes [1–6] have been synthesized with ligands L1 (L1 = Pyridin-2-ylmethylene picolinichydrazine) and L2 (L2 = Pyridin-3-ylmethylene picolinichydrazine). Treatment of [{Cp∗MCl2}2] (M = Rh/Ir) with L1 in methanol has yielded mononuclear cationic complexes such as [{Cp∗M(L1N∩N)Cl}]PF6 where {M = Rh (1) and Ir (2)} and dinuclear complexes such as [{(Cp∗MCl)2(L1N∩N, N∩N)}]PF6 where {M = Rh (3) and Ir (4)} in 1:2 and 1:1 metal dimer to ligand ratios respectively. Reactions of [{Cp∗MCl2}2] with L2 in both 1:2 and 1:1 metal dimer to ligand ratios have yielded two metalla-macrocyclic dinuclear and dicationic complexes such as [{Cp∗M(L2N∩NμN)}2](PF6)2 where {M = Rh (5) and Ir (6)}. Spectroscopic and crystallographic data were used to elucidate the structures of the synthesized complexes. The in vitro antitumor evaluation of the complexes 1 and 2 by fluorescence based apoptosis study revealed their antitumor activity against Dalton’s ascites lymphoma (DL) cells. The antibacterial evaluation of complexes 1, 2, 5 and 6 by agar well-diffusion method revealed their significant activity against the two species considered viz., Proteus vulgaris (MTCC 426) and Vibrio parahaemolyticus (MTCC 451) with zone of inhibition up to 43 mm. The docking study with few key enzymes associated with cancer viz., ribonucleotide reductase, thymidylate synthase, thymidylate phosphorylase and topoisomerase II revealed their strong interactions with complexes under study. Complexes 1–6 exhibited a HOMO (highest occupied molecular orbital) – LUMO (lowest unoccupied molecular orbital) energy gap from 2.95 eV to 3.59 eV. TDDFT calculations explain the nature of electronic transitions and found well agreement with the experiments. Keywords: Rhodium dimer, Pyridin-2-ylmethylene picolinichydrazine, Metalla-macrocycles, Antitumor, Antibacterial, TDDFT

Derivatives of thiazole-pyrazole fused benzo-coumarin compounds were successfully synthesized and characterized, followed by a comprehensive spectroscopic investigation on various photophysical properties in different media. The multipronged approach using steady state and time resolved fluorescence spectroscopy pointed out the impact of substitution in the estimated spectroscopic and other physicochemical properties of the systems. Further, the evaluation of anti-acetylcholinesterase (anti-AChE) activity yielded significant insight into the therapeutic potential of the synthesized coumarinyl compounds for the treatment of Alzheimer's disease (AD). The findings revealed a non-competitive mode of inhibition mechanism, with an estimated IC 50 value of 67.72 ± 2.00 nM observed for one of the investigated systems as AChE inhibitor. Notably, this value is even lower than that of an FDA-approved AD drug Donepezil (DON), indicating the enhanced potency of the coumarin derivatives in inhibiting AChE. Interestingly, significant diminution in inhibition was observed in presence of human serum albumin (HSA) as evidenced by the relative increase in IC 50 value by 8 ∼ 39 % in different cases, which emphasized the role of albumin proteins to control therapeutic efficacies of potential medications. In-depth spectroscopic and in-silico analysis quantified the nature of interactions of the investigated systems with HSA and AChE. Overall, the outcomes of this study provide significant understanding into the biophysical characteristics of novel thiazole-pyrazole fused benzo-coumarin systems, which could aid in the development of new cholinergic agents for the treatment of AD and materials based on coumarin motifs., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023. Published by Elsevier B.V.)

Amine transaminases (ATA) convert ketones into optically active amines and are used to prepare active pharmaceutical ingredients and building blocks. Novel ATA can be identified in protein databases due to the extensive knowledge of sequence-function relationships. However, predicting thermo- and operational stability from the amino acid sequence is a persisting challenge and a vital step towards identifying efficient ATA biocatalysts for industrial applications. In this study, we performed a database mining and characterized selected putative enzymes of the β-alanine:pyruvate transaminase cluster (3N5M) - a subfamily with so far only a few described members, whose tetrameric structure was suggested to positively affect operational stability. Four putative transaminases (TA-1: Bilophilia wadsworthia, TA-5: Halomonas elongata, TA-9: Burkholderia cepacia, and TA-10: Burkholderia multivorans) were obtained in a soluble form as tetramers in E. coli. During comparison of these tetrameric with known dimeric transaminases we found that indeed novel ATA with high operational stabilities can be identified in this protein subfamily, but we also found exceptions to the hypothesized correlation that a tetrameric assembly leads to increased stability. The discovered ATA from Burkholderia multivorans features a broad substrate specificity, including isopropylamine acceptance, is highly active (6 U/mg) in the conversion of 1-phenylethylamine with pyruvate and shows a thermostability of up to 70 °C under both, storage and operating conditions. In addition, 50% (v/v) of isopropanol or DMSO can be employed as co-solvents without a destabilizing effect on the enzyme during an incubation time of 16 h at 30 °C. KEY POINTS: • Database mining identified a thermostable amine transaminase in the β-alanine:pyruvate transaminase subfamily. • The tetrameric transaminase tolerates 50% DMSO and isopropanol under operating conditions at 30 °C. • A tetrameric structure is not necessarily associated with a higher operational stability., (© 2022. The Author(s).)

The main objective of this review is to give a general overview of the structure, electrochemistry (when available), and catalytic performance of the Ru complexes, which are capable of oxidizing water to molecular dioxygen, and to highlight their more relevant features. The description of the Ru catalysts is mainly divided into complexes that contain a Ru-O-Ru bridging group and those that do not. Finally a few conclusions are drawn from the global description of all of the catalysts presented here, and some guidelines for future catalyst design are given.