A series of novel ruthenium(II) arene RAPTA type derivatives (arene = cymene, hexamethylbenzene) containing curcumin-based ligands (curcH = curcumin, bdcurcH = bisdemethoxycurcumin) and PTA (1,3,5-triaza-7-phosphaadamantane) have been synthesized and fully characterized. The solid-state structures of [Ru(cym)(curc)(PTA)][SO₃CF₃], [Ru(hmb)(curc)(PTA)][SO₃CF₃], and [Ru(hmb)(bdcurc)(PTA)][SO₃CF₃] have been determined by single-crystal X-ray diffraction. The antitumor activity of the complexes has been evaluated in vitro against human ovarian carcinoma cells (A2780 and A2780cisR), as well as against nontumorous human embryonic kidney (HEK293) cells. The correlation of the cytotoxicity upon switching the curcumin-based ligands, i.e. curcumin vs bisdemethoxycurcumin, is not straightforward. In contrast, the PTA ligand greatly enhances the activity and selectivity of ruthenium compounds in comparison to previously reported compounds.

Four new mononuclear Ni(II) complexes [Ni(L¹)]ClO₄ (1a), [Ni(L²)]ClO₄(1b), [Ni(SCN)₃(CH₃OH)(aminoethylpiperazineH)] (2a), and [Ni(DMSO)₄(aminoethylpiperazineH)](ClO₄)₃(2b)have been synthesized from two Schiff base ligands [L¹ = 1-phenyl-3-((2-(piperidin-4-yl)ethyl)imino)but-1-en-1-ol and L² = 4-((2-(piperazin-1-yl)ethyl)imino)pent-2-en-2-ol] by exploiting the flexibility of the piperazinyl moiety. Structural analysis reveals that 1a and 1b are square planar complexes with piperazine rings in boat conformations whereas hydrolysis of Schiff bases (L¹ and L²) occurs during formation of octahedral complexes (2a and 2b) with piperazine rings in chair conformations. Screening tests were conducted to quantify the binding ability of complexes (1a, 1b and 2a) towards DNA, BSA and HSA and it was found that square planar complexes (1a and 1b) showed more effective binding properties over octahedral complex (2a). Furthermore, enzyme kinetic studies reflect that square planar complexes (1a and 1b) are also effective in mimicking catecholase like activities over octahedral complex (2a). Among all the complexes, 1a was found to be the most promising molecule among the series due to its large binding affinity towards different bio-macromolecules and higher T.O.N in the catechol oxidation reaction.

With the discovery of cisplatin, a vast area of applications of metallodrugs in cancer treatment was opened but due to the side effects caused by the cisplatin complexes, researchers began to look for alternatives with similar anticancer properties but fewer side effects. Ruthenium was found to be a promising candidate, considering its significant anticancer properties and low side effects. Several ruthenium complexes, viz. NAMI-A, KP1019, KP1339, and TLD1433, have entered clinical trials. Some other arene ruthenium complexes such as RM175 and RAPTA-C have also entered clinical trials but very few of them have shown anti-metastatic properties. Herein, we provide information and probable mechanistic pathways for ruthenium(II)–arene complexes that have been studied, so far, for their anti-metastatic activities. Also, we discuss the techniques and their significance for determining the anti-metastatic effects of the complexes.

Non-steroidal anti-inflammatory drugs (NSAIDs) are a group of molecules which have been found to be active against cancer cells with chemopreventive properties by targeting cyclooxygenase (COX-1 and COX-2) and lipoxygenase (LOX), commonly upregulated (particularly COX-2) in malignant tumors. Arene ruthenium(II) complexes with a pseudo-octahedral coordination environment containing different ancillary ligands have shown remarkable activity against primary and metastatic tumors as reported earlier. This work describes the synthesis of four novel ruthenium(II)–arene complexes viz. [Ru(η⁶-p-cymene)(nap)Cl] 1 [Hnap = naproxen or (S)-2-(6-methoxy-2-naphthyl)propionic acid], [Ru(η⁶-p-cymene)(diclo)Cl] 2 [Hdiclo = diclofenac or 2-[(2,6-dichlorophenyl)amino] benzeneacetic acid, [Ru(η⁶-p-cymene)(ibu)Cl] 3 [Hibu = ibuprofen or 2-(4-isobutylphenyl)propanoic acid] and [Ru(η⁶-p-cymene)(asp)Cl] 4 [Hasp = aspirin or 2-acetoxy benzoic acid] using different NSAIDs as chelating ligands. Complexes 1–3 have shown promising antiproliferative activity against three different cell lines with GI₅₀ (concentration of drug causing 50% inhibition of cell growth) values comparable to adriamycin. At the concentration of 50 μM, complex 3 is more effective in the inhibition of cyclooxygenase and lipooxygenase enzymes, followed by complex 2 and complex 1 in comparison to their respective free NSAID ligands indicating a possible correlation between the inhibition of COX and/or LOX and anticancer properties. Molecular docking studies with COX-2 reveal that complexes 1 and 2 having naproxen and diclofenac ligands exhibit stronger interactions with COX-2 than their respective free NSAIDs and these results are in good agreement with their relative experimentally observed COX inhibition as well as anti-proliferative activities.

Two new metal–organic compounds {[Cu₃(μ₃-4-ptz)₄(μ₂-N₃)₂(DMF)₂](DMF)₂}_n (1) and {[Cu(4-ptz)₂(H₂O)₂]}_n (2) {4-ptz = 5-(4-pyridyl)tetrazolate} with 3D and 2D coordination networks, respectively, have been synthesized while studying the effect of reaction conditions on the coordination modes of 4-pytz by employing the [2 + 3] cycloaddition as a tool for generating in situ the 5-substituted tetrazole ligands from 4-pyridinecarbonitrile and NaN₃ in the presence of a copper(II) salt. The obtained compounds have been structurally characterized and the topological analysis of 1 discloses a topologically unique trinodal 3,5,6-connected 3D network which, upon further simplification, results in a uninodal 8-connected underlying net with the bcu (body centred cubic) topology driven by the [Cu₃(μ₂-N₃)₂] cluster nodes and μ₃-4-ptz linkers. In contrast, the 2D metal–organic network in 2 has been classified as a uninodal 4-connected underlying net with the sql [Shubnikov tetragonal plane net] topology assembled from the Cu nodes and μ₂-4-ptz linkers. The catalytic investigations disclosed that 1 and 2 act as active catalyst precursors towards the microwave-assisted homogeneous oxidation of secondary alcohols (1-phenylethanol, cyclohexanol, 2-hexanol, 3-hexanol, 2-octanol and 3-octanol) with tert-butylhydroperoxide, leading to the yields of the corresponding ketones up to 86% (TOF = 430 h⁻¹) and 58% (TOF = 290 h⁻¹) in the oxidation of 1-phenylethanol and cyclohexanol, respectively, after 1 h under low power (10 W) microwave irradiation, and in the absence of any added solvent or additive.