Anticancer properties, apoptosis and catecholase mimic activities of dinuclear cobalt(II) and copper(II) Schiff base complexes.

The present work describes coordination chemistry and biological evaluation of two novel dinuclear complexes [Co2(HL1)2(H2O)2]·8H2O (1) and [Cu2(L2)2] (2) obtained from the Schiff base ligands, H3L1 and H2L2 (formed in situ). The two complexes are characterized by single crystal X-ray, spectral and variable temperature magnetic and theoretical (DFT/TDDFT) analysis. X-ray analysis confirms both the complexes to be dinuclear with distorted octahedral and square pyramidal geometry around Co(II) and Cu(II) ions, respectively. Magnetic studies reveal presence of moderate ferromagnetic interactions in both the complexes with J = 98 (1) and 32 (2) cm-1. The magnetic interactions are further corroborated by DFT studies. Co(II) complex (1) exhibited enhanced catecholase activity with Kcat = 213.48 h-1, which is attributed to the greater extent of charge contribution on Co2+ as compared to Cu2+ as determined by DFT calculations. Furthermore, both the complexes show potent anticancer activity toward HeLa (cervical) and A549 (lung) cancer cell lines with IC50 = 6-7 µM at 48 h, which ascertains both the complexes as better anticancer drugs than cisplatin. Furthermore, 1 and 2 exhibit apoptosis of HeLa cells by demonstrating nuclear blebbings with shrinking morphology. Hence, the present complexes could be employed as a model for metalloenzymes as well as potential anticancer substituents of cisplatin in future course.

How to identify a smoker: a salient crystallographic approach to detect thiocyanate content.

There is an increasing demand for monitoring environmental pollutants and the control requires new sensing materials with better sensitivity, selectivity and reliability. In this study, a series of Co7 clusters incorporating various flexible polyhydroxyamine ligands are explored, with the first report of thiocyanate recognition triggered by crystal formation using a Co7 crystal (1). For this, we have fortunately synthesized three new mixed metal Co7 clusters with fascinating structural features. The clusters were characterized by spectroscopic and single crystal X-ray diffraction methods and later by DFT calculations. Due to its better emission spectrum, 1 was further utilized for evaluating its sensing ability towards various anions in water. Surprisingly, 1 shows better quenching ability towards the recognition of SCN- with a better binding constant. The luminescence quenching towards SCN- detection was further verified by the single crystal method, HSAB principle (symbiosis) and theoretical calculations such as DFT studies. The SCXRD data clearly suggest that the Co7 (1) can be converted into Co14 (1a) by direct reaction with NaSCN under ambient conditions. Besides the soft/hard acid-base concept (symbiosis), the energies of formation, and Co-NCS and Co-OH2 bond energies (as unravelled by DFT) are responsible for this transformation. Therefore, 1 can be used as a selective and sensitive sensor for the detection of thiocyanate anions based on the fluorescence amplification and quenching method. Further, the designed cluster has also been utilized to detect anions in human blood samples to differentiate a smoker and a non-smoker. It has been concluded that the samples of smokers have a high degree of thiocyanate (∼12 or 9.5 mg L-1) in comparison to those of non-smokers (2-3 mg L-1). Thus, this kind of cluster material has high potentiality in the field of bio-medical science in future endeavours for identification of the extent of thiocyanate content in smokers.

Novel {Cu4} and {Cu4Cd6} clusters derived from flexible aminoalcohols: synthesis, characterization, crystal structures, and evaluation of anticancer properties.

Two new copper clusters, {Cu4} and {Cu4Cd6}, with polydentate aminoalcohol ligands, diethanol propanolamine (H3L1) and bis-tris{2-[bis(2-hydroxyethyl)amino]-2-(hydroxymethyl)propane-1,3-diol} (H6L2), have been synthesized under mild conditions and characterized thoroughly by single-crystal X-ray diffraction (XRD), infrared spectroscopy, elemental analysis, powder XRD, magnetic and DFT studies, and absorption and fluorescence spectroscopy. The cluster {Cu4} exhibits a rare tetranuclear copper cubane core whereas {Cu4Cd6} forms an unusual heterometallic cage owing to the introduction of the second metal Cd into the ligand. A hexapodal ligand (H6L2) with N and O donor atoms was chosen deliberately for the construction of a high-nuclearity cluster, i.e., {Cu4Cd6}. Interestingly, both the clusters displayed significant cytotoxicity towards human cervical (HeLa) and lung (A549) cancer cells as evident from the shallow IC50 values [15.6 ± 0.8 µM (HeLa), 18.5 ± 1.9 µM (A549) for {Cu4}, and 11.1 ± 1.5 µM (HeLa), 10.2 ± 1.3 µM (A549) for {Cu4Cd6}] obtained after a 24 h incubation. However, moderate toxicity was observed toward immortalized lung epithelial normal cells (HPL1D) with IC50 values of 32.4 ± 1.2 µM for {Cu4} and 27.6 ± 1.7 µM for {Cu4Cd6}. A cellular apoptotic study using HeLa cells revealed that the {Cu4} cluster triggered apoptosis at both the early and late phases while the {Cu4Cd6} cluster facilitate apoptosis mainly at the late apoptotic stage. A standard 2',7'-dichlorodihydrofluorescein-diacetate (DCFH-DA) test affirms that both the clusters enhanced ROS production inside the cancer cells, responsible for promoting cell apoptosis. The decanuclear {Cu4Cd6} clusters demonstrated better anticancer activity compared to the tetranuclear {Cu4} clusters, indicating the role of high nuclearity and additional Cd metal in the enhanced intracellular production of ROS.

A novel self-assembled Na{Cu12Zn4} multifunctional material: first report of a discrete coordination compound for detection of Ca2+ ions and selective adsorption of cationic dyes in water.

A novel metal directed discrete self-assembled compound, Na2O[Cu12Zn4(µ-OH)8(H4btp)8](ClO4)8·26H2O (1), was synthesized employing a flexible aminoalcohol ligand, 2,2'-(propane-1,3-diyldiimino)bis-[2-(hydroxylmethyl)propane-1,3-diol] (H6btp), and mixed metal ions (CuII and ZnII) in order to explore it as a multifunctional material. The molecular cluster is characterized by spectral and analytical techniques, single crystal X-ray diffraction and magnetic studies. Crystallography reveals the presence of eight peripheral CuII centers in octahedral environments, while four interior CuII and ZnII centers are present in tetrahedral systems. The ligand is coordinated in the dianionic form (H4btp2-) with copper and zinc metal ions through various bridging modes. Magnetic data suggest the presence of strong antiferromagnetic coupling between the twelve Cu(ii) centers (C = 4.31 cm3 K mol-1 and θ = -120.44 K). Interestingly, the eight ligands present in the system have eight free hydroxyl groups at the periphery of the cluster, which could be employed in molecular recognition for the analytes under investigation. One of the sodium cations of the lattice sodium oxide [Na2O or Na+(Na+O2-)] is encapsulated in the {Cu12Zn4} cavity and held through electrostatic interactions with the oxygen atoms, forming a Na{Cu12Zn4} core. Taking advantage of this entrapped cation, we have used the present assembly in the sensing of various s-block cations. Interestingly, the cluster shows a sensitive and selective sensing ability towards Ca2+ ions through cation exchange. The selectivity towards Ca2+ can be rationalized in terms of the identical size of the sodium and calcium ions and the HSAB principle. Hard sodium is exchanged with the hard Ca2+ ion, which effectively interacts with the hard oxygen donor, giving rise to a stable hard-hard interaction. Moreover the Na{Cu12Zn4} cluster shows excellent selectivity towards the adsorption of cationic dyes, specifically methylene blue (MB), via non-covalent interactions. An abundance of free O-H groups in the cluster gives rise to the existence of O-Hπ interactions with the dye for enhanced adsorption. Thus, the present report is the first example of any heterometallic coordination compound (in contrast to complex systems like polymeric frameworks/nanocomposites) with discriminating sensing of Ca2+ ions with ultra-low detection limit (4 nM) and with high efficiency in the selective adsorption and separation of methylene blue.