Mixed-ligand cobalt(II) complexes of bioinorganic and medicinal relevance, involving dehydroacetic acid and β-diketones: Their synthesis, hyphenated experimental-DFT, thermal and bactericidal facets

Dehydroacetic acid a privileged medicinal scaffold: A concise review

From the last decade, research on dehydroacetic acid (DHA) and its derivatives has increased immensely due to its significant role in various fields, including medicine, cosmetics, food industry, and so on. In the medicinal area, DHA plays an essential role in developing novel action-based drugs, which are helpful for treating various diseases. Besides its plethora of biological applications, its chelating ability offers the easiest synthetic route for synthesizing more active metal complexes. DHA derivatives along with their metal complexes show a number of biological activities and also exhibit various interactions with multiple biological targets. This article summarizes recent medicinal applications (2000-onwards) of DHA-based compounds and their analogs, along with their structure-activity relationship (SAR) analysis. Their interactions with different target enzymes are also discussed. This information derived from SAR analysis would be helpful for medicinal chemists working on the development of drugs based on heterocyclic frameworks, particularly those based on the DHA scaffold.

Frequency-dependent nonlinear optical response and refractive index investigation of lactone-derived thermochromic compounds

Nonlinear optical (NLO) switchable materials play a crucial role in the fields of electronics and optoelectronics. The selection of an appropriate switching approach is vital in designing such materials to enhance their NLO response. Among various approaches, thermos-switching materials have shown a 4-fold increase in NLO response compared to other photo-switching materials. In this study, we computationally investigated the geometric, electronic, and nonlinear optical properties of reversible lactone-based thermochromic compounds using the ωB97XD/6-311+G (d,p) level of theory. Molecular orbital studies are employed to analyze the electronic properties of the close and open isomers of these compounds, while time-dependent density functional theory (TD-DFT) analysis is utilized to evaluate their molecular absorption. Our findings reveal that the π-electronic conjugation-induced delocalization significantly influences the ON-OFF switchable nonlinear optical response of the lactone-based thermochromic compounds. Notably, among all compounds, the open isomer of lactone 2 exhibits the highest hyperpolarizability value (6596.69 au). Furthermore, we extended our analysis to investigate the frequency-dependent second and third-order hyperpolarizabilities. The most pronounced frequency-dependent NLO response is observed at 532 nm. Additionally, we calculated the refractive index of these thermochromic compounds to further assess their nonlinear optical response. The open isomer of lactone 1 demonstrates the highest refractive index value (3.99 × 10-14 cm2/W). Overall, our study highlights the excellent potential of reversible thermochromic compounds as NLO molecular thermos-switches for future applications.

The Role of Redox Potential and Molecular Structure of Co(II)-Polypyridine Complexes on the Molecular Catalysis of CO2 Reduction

In this work, we report the electrochemical response of a family of Co(II) complexes, [CoII(L)3]2+ and [CoII(L’)2]2+ (L = 2,2’-bipyridine, 1,10-phenanthroline, 3,4,7,8-tetramethyl-1,10-phenanthroline, 5,6-dimethyl-1,10-phenanthroline, and 4,7-diphenyl-1,10-phenanthroline; L’ = terpyridine and 4-chloro-terpyridine), in the presence and absence of CO2 in order to understand the role of the redox potential and molecular structure on the molecular catalysis of CO2 reduction. The tris chelate complexes exhibited three electron transfer processes [CoII(L)3]2+ ⇄ [CoIII(L)3]3+ + 1e−, [CoΙΙ(L)3]2++1e− ⇄ [CoΙ(L)3]+, and [CoΙ(L)3]+ + 2e- ⇄ [CoΙ(L)(L−)2]−. In the case of complexes with 1,10-phen and 2,2-bipy, the third redox process showed a coupled chemical reaction [CoΙ(L)(L−)2]− → [CoΙ(L−)2]− + L. For bis chelate complexes, three electron transfer processes associated with the redox couples [CoΙΙ(L)2]/[CoIII(L)2]3+, [CoΙΙ(L)2]2+/[CoΙ(L)2]+, and [CoΙ(L)2]+/[CoΙ(L)(L−)] were registered, including a coupled chemical reaction only for the complex containing the ligand 4-chloro-terpyridine. Foot to the wave analysis (FOWA) obtained from cyclic voltammetry experiments allowed us to calculate the catalytic rate constant (k) for the molecular catalysis of CO2 reduction. The complex [Co(3,4,7,8-tm-1,10-phen)3]2+ presented a high k value; moreover, the complex [Co(4-Cl-terpy)3]2+ did not show catalytic activity, indicating that the more negative redox potential and the absence of the coupled chemical reaction increased the molecular catalysis. Density functional theory (DFT) calculations for compounds and CO2 were obtained to rationalize the effect of electronic structure on the catalytic rate constant (k) of CO2 reduction.

Nitric oxide functionalized molybdenum(0) pyrazolone Schiff base complexes: thermal and biochemical study

This work describes the synthesis and characterization of three molybdenum dinitrosyl Schiff base complexes of the general formula [Mo(NO)₂(L)(OH)], where L is N-(dehydroacetic acid)-4-aminoantipyrene (dha-aapH), N-(4-acetylidene-3-methyl-1-phenyl-2-pyrazolin-5-one)-4-aminoantipyrine (amphp-aapH) or N-(3-methyl-1-phenyl-4-propionylidene-2-pyrazolin-5-one)-4-aminoantipyrine (mphpp-aapH). The complexes were formulated on the basis of spectroscopic analyses, elemental composition, magnetic susceptibility measurements, molar conductance behaviour and determination of the respective decomposition temperatures. A comparative experimental-theoretical approach was followed to elucidate the structure of the complexes. Fourier transform infra-red (FT-IR) spectroscopy, thermo-gravimetry (TG) and electronic spectral insights were mainly focused on the confirmation of the formation of the complexes. The computational density functional theory (DFT) calculations evaluated in the study involve the molecular specification for the use of LANL2DZ/RB3LYP formalism for metal atoms and 6-311G/RB3LYP for the remaining non-metal atoms. The study reveals a suitable cis-octahedral geometry for the complexes. The TG curve of one of the representative complexes was evaluated to find the respective thermodynamic and kinetic parameters using various physical methods. The Freeman & Carroll (FC) differential method, the Horowitz and Metzger (HM) approximation method, the Coats–Redfern method and the Broido method were employed to present a comparative thermal analysis of the complex. The Broido method proved the best fit to the results for the compound under question. In addition to structural and thermal analyses, the study also deals with the in vitro antimicrobial and anticancer sensitivity of the complexes. The results revealed potent biological properties of the representative complex containing dha-aapH. Cell toxicity tests against COLO-205 human cancer cell line using a 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide (MTT) assay showed an IC₅₀ value of 53.13 μgm mL⁻¹ for the Schiff base and 10.51 μgm L⁻¹ for the respective complex. Similarly the same complex proved to be an effective antimicrobial agent against Aspergillus, Pseudomonas, E. coli and Streptococcus. The results indicated a more pronounced activity against Pseudomonas and Streptococcus than the other two microbial species.

This work describes the thermal and biological implications of three pyrazolone-dinitrosylmolybdenum(0) complexes.