Two tetragonal molecular barrels TB1 and TB2 were successfully synthesized by coordination-driven self-assembly of a tetrapyridyl donor ( L ) of the thiazolo[5,4- d ]thiazole backbone with cis -blocked 90° Pd(II) and Pt(II) acceptors, respectively. The single-crystal structure analysis of TB1 revealed the formation of a two-face opened tetragonal Pd 8 molecular barrel architecture. In contrast, the isostructural Pt(II) barrel ( TB2 ) is water-soluble. The large confined hydrophobic molecular cavity including wide open windows and good water solubility of the barrel TB2 made it a potential molecular container for the encapsulation of guests with different sizes and properties. This has been exploited to encapsulate and stabilize the open form of a photochromic molecule ( G2 ) in water, while the same photochromic molecule exists exclusively in a cyclic zwitterionic form in aqueous medium in the absence of the barrel TB2 . This cyclic form is very stable in water and does not go back to its parent open form under common external stimuli. Surprisingly, reverse switching of the cyclic form to a colored hydrophobic open form was also possible instantly in water upon addition of the solid barrel TB2 into an aqueous solution of G2 . Such a fast reverse isomerization of an irreversible process in aqueous medium by utilizing host–guest interaction of the barrel TB2 and the guest G2 is interesting. The barrel TB2 was also capable of encapsulating the water-insoluble radical initiator G1 in aqueous medium.

The synthesis, structures, and magnetic properties of two heterometallic Cu(II)-Dy(III) clusters are reported. The first structural motif displays a pentanuclear Cu(II)4Dy(III) core, while the second one reveals a nonanuclear Cu(II)6Dy(III)3 core. We employed o-vanillin-based Schiff base ligands combining o-vanillin with 3-amino-1-propanol, H2vap, (2-[(3-hydroxy-propylimino)-methyl]-6-methoxy-phenol), and 2-aminoethanol, H2vae, (2-[(3-hydroxy-ethylimino)-methyl]-6-methoxy-phenol). The differing nuclearities of the two clusters stem from the choice of imino alcohol arm in the Schiff bases, H2vap and H2vae. This work is aimed at broadening the diversity of Cu(II)-Dy(III) clusters and to perceive the consequence of changing the length of the alcohol arm on the nuclearity of the cluster, providing valuable insight into promising future synthetic directions. The underlying topological entity of the pentanuclear Cu4Dy cluster is reported for the first time. The investigation of magnetic behaviors of 1 and 2 below 2 K reveals slow magnetic relaxation with a significant influence coming from the variation of the alcohol arm affecting the nature of magnetic interactions.

We have synthesized and structurally characterized a new doubly chloro bridged dimeric copper(II) complex, [Cu2(μ-Cl)2(HL)2Cl2] (1) based on a Schiff base ligand, 5-[(pyridin-2-ylmethylene)-amino]-pentan-1-ol). Single crystal X-ray diffraction shows the presence of dinuclear copper(II) centres in a square pyramidal geometry linked by obtuse double chloro bridge. The magnetic study illustrated that weak antiferromagnetic interactions (J = -0.47 cm(-1)) prevail in complex 1 which is well supported by magneto-structural correlation. This compound adds to the library of doubly chloro bridged copper(ii) complexes in the regime of spin state cross over. DFT calculations have been conducted within a broken-symmetry (BS) framework to investigate the exchange interaction further which depicts that the approximate spin projection technique yields the best corroboration of the experimental J value. Spin density plots show the presence of an ∼0.52e charge residing on the copper atom along with a substantial charge on bridging and peripheral chlorine atoms. The potential of complex1 to act as an anticancer agent is thoroughly examined on a series of liver cancer cell lines and screening shows the HepG2 cell line exhibits maximum cytotoxicity by phosphatidyl serine exposure in the outer cell membrane associated with ROS generation and mitochondrial depolarization with increasing time in the in vitro model system.

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A reaction of N,N-bis(3-methoxysalicylidene) diethylenetriamine (H2Vd) and Zn(NO)·6HO, ZnBr, ZnI and Cd(NO)·4HO in a methanol solution led to zinc and cadmium complexes of different nuclearities, [Zn(Vd·H)(X)]·CHOH (X = NO, Br, I) [1a, 1b and 1c] and Cd(Vd)(NO) (2). In 1(a-c), two H2Vd ligands bridge the two metal centers whereas in 2, they provide sideways support to two terminal Cd ions, providing an all-oxygen envelope to the central Cd ion. All four compounds were characterized by elemental analysis, FT-IR spectroscopy and single crystal X-ray diffraction analysis. Complexes 1(a-c) exhibit dinuclear structures, whereas 2 exhibits a nearly linear trinuclear structure. The structural differences among these complexes are attributable to various coordination modes and flexible configurations of the H2Vd ligand. The ligand H2Vd is an excellent probe for sensing Zn in solution, whereas complexes 1(a-c) are able to selectively detect pyrophosphate (PPi) in aqueous medium. The structure of the pyrophosphate (PPi) complex has been proposed using DFT calculations and the selectivity is due to the unique ability of this anion to simultaneously coordinate to both the Zn metal centers. The anticancer activity of complexes 1(a-c) was also explored.