Introduction 4658 2. Functionalization at the 1,3-Positions of Calix[4]arene 4659 3. Cation Receptors 4660 3.1. Zn 2þ Recognition 4660 3.1.1. Receptors Possessing Imino-phenolic Core 4660 3.1.2. Imino-phenolic Core Linked through Triazole Moiety 4661 3.1.3. Receptors Possessing Cores Other than the Imino-phenolic Ones 4661 3.2. Cu 2þ Recognition 4663 3.2.1. Cyclic Conjugates 4663 3.2.2. Noncyclic Conjugates 4664 3.3. Monomer/Excimer Emissions in the Presence of Fe 3þ 4666 3.4. Hg 2þ Recognition 4666 3.4.1. Cyclic Conjugates 4666 3.4.2. Noncyclic Conjugates 4667 3.5. Pb 2þ Recognition 4670 3.6. Ag þ Recognition 4671 3.7. Al 3þ Recognition 4673 3.8. Recognition of Alkali Metal Ions 4673 3.9. Recognition of Alkaline Earth Metal Ions 4676 3.10. Lanthanide Ion Recognition 4678 4. Anion Receptors 4680 4.1. Inorganic Anions 4680 4.1.1. Fluoride Recognition 4680 4.1.2. Chloride Recognition 4681 4.1.3. Iodide Recognition 4682 4.1.4. Chromate Recognition 4682 4.1.5. HSO 4 À and HSO 3 À Recognition 4683 4.1.6. Phosphate Recognition 4684 4.1.6.1. Recognition of Phosphate by Uncomplexed Calix[4]arene Conjugates 4684 4.1.6.2. Recognition of Phosphate by a Metal Complex of Calix[4]arene Conjugate 4686 4.2. Organic Anions 4687 4.2.1. Acetate Recognition 4687 4.2.2. Recognition by Dicarboxylates 4688 4.3. Chiral Recognition by Calix[4]arene Conjugates 4689 5. Amino Acids and Other Molecular Recognition 4693 5.1. Recognition of Amino Acids by Uncomplexed Calix[4]arene Conjugates 4693 5.2. Recognition of Amino Acid by Metal Complexes of the Calix[4]arene Conjugates 4694 5.3. Recognition of Other Molecular Species 4695 6. Conclusions and Future Perspectives 4697 Author Information 4698 Biographies 4698 Acknowledgment 4698 List of Abbreviations 4698 References 4699

Amide linked lower rim 1,3-dibenzimidazole derivative of calix[4]arene, L has been shown to be sensitive and selective to Hg(2+) in aqueous acetonitrile solution based on fluorescence spectroscopy, and the stoichiometry of the complexed species has been found to be 1:1. The selectivity of L toward Hg(2+) has been shown among 11 M(2+) ions, viz., Mn(2+), Fe(2+), Co(2+), Ni(2+), Cu(2+), Zn(2+), Cd(2+), Hg(2+), Pb(2+), Ca(2+), and Mg(2+) studied, including those of the mercury group and none of these ions impede the recognition of Hg(2+) by L. Role of the solvent on the recognition of Hg(2+) has been demonstrated. The role of calix[4]arene platform and the benzimidazole moieties in the recognition of Hg(2+) by L has been delineated upon performing such studies with five different molecules of relevance as reference molecular systems. The binding cores formed by the receptor L and the reference compounds have been established based on the single crystal XRD structures, and the preferential metal ion binding cores have been discussed. The binding of Hg(2+) with L has been further established based on (1)H and (13)C NMR, ESI MS, absorption, and fluorescence lifetime measurements. Some of these techniques have been used to establish the stoichiometry of the species formed. The complex species formed between L and Hg(2+) have been isolated and characterized and found to be 1:1 species even in the isolated complex. Whereas transmission electron microscopy (TEM), atomic force microscopy (AFM), and scanning electron microscopy (SEM) provided the nanostructural behavior of L, the TEM and SEM demonstrated that the mercury complex has different characteristics when compared to L. The TEM, SEM, and powder XRD studies revealed that whereas L is crystalline, that of the mercury complex is not, perhaps a reason for not being able to obtain single crystals of the complex. Binding characteristics of Hg(2+) toward L have been established based on the DFT computational calculations.

A large variety of oxovanadium(V) complexes, mononuclear VO(2)(+) and VO(3+) in addition to the dinuclear VO(3+), of the structural type (VOL)(2), (VOHL)(2), VOLHQ, K(VO(2)HL), K(VO(2)H(2)L), or (salampr) (VO(2)L) {where L = Schiff base ligand possessing alkoxo group(s); HQ = 8-hydroxyquinoline; salampr = cation of reduced Schiff base derived from salicylaldehyde and 2-amino-2-methylpropan-1-ol}, bound to alkoxo, phenolate and imine groups have been synthesized in high yields and characterized by several spectral and analytical methods, including single crystal X-ray studies. While the mononuclear VO(2)(+) complexes have been synthesized at alkaline pH, the dinuclear VO(3+) complexes have been synthesized under neutral conditions using alkoxo rich Schiff base ligands. The X-ray structures indicate that the cis-dioxo complexes showed longer V-O(alkoxo) bond lengths compared to the monooxo counterparts. The plot of V-O(phen) bond distances of several VO(3+) complexes vs the lmct showed a near linear correlation with a negative slope. The cyclic voltammograms revealed a reversible V(V)/V(IV) couple with the reduction potentials increasing to more negative ones as the number of alkoxo groups bound to V increases from 1 to 2. Moreover, the cis-dioxo VO(2)(+) complexes are easier to reduce than their monooxo counterparts. The solution stability of these complexes was studied in the presence of added water (1:4, water:solvent), where no decomposition was observed, unlike other Schiff base complexes of V. The conversion of the dioxo complexes to their monooxo counterparts in the presence of catalytic amounts of acid is also demonstrated. The reactivity of alkoxo bound V(V) complexes is also reported. X-ray parameters are as follows. H(4)L(3): monoclinic space group, P2(1)/c; a = 10.480(3), b = 8.719(6), c = 12.954(8) Å; beta = 101.67(4) degrees; V = 1126(1) Å(3); Z = 4; R = 0.060, R(w) = 0.058. Complex 1: monoclinic space group, P2(1)/n; a = 12.988(1), b = 9.306(2), c = 19.730(3) Å; beta = 99.94(1) degrees; V = 2348.9(7) Å(3); Z = 4; R = 0.031, R(w) = 0.027. Complex 2: monoclinic space group, P2(1)/n; a = 12.282(3), b = 11.664(2), c = 12.971(4) Å; beta = 97.89(2) degrees; V = 1840.5(8) Å; Z = 4; R = 0.035, R(w) = 0.038. Complex 5: monoclinic space group, P2(1)/c; a = 17.274(2), b = 6.384(2), c = 16.122(2) Å; beta = 116.67(1) degrees; V = 1588.7(7) Å(3); Z = 4; R = 0.039, R(w) = 0.043. Complex 8: monoclinic space group, P2(1)/c; a = 11.991(1), b = 11.696(4), c = 12.564(3) Å; beta = 110.47(1) degrees; V = 1650.8(8) Å(3); Z = 2; R = 0.045, R(w) = 0.049.

Metallo-organic compounds are interesting to study for their antitumor activity and related applications. This paper deals with the syntheses, characterization, structure determination of a copper complex of anthracenyl terpyridine (1) and its plasmid cleavage and cytotoxicity towards different cancer cell lines. The complex binds CT-DNA through partial intercalation mode. The plasmid cleavage studies carried out using pBR322 and pUC18 resulted in the formation of all the three forms of the plasmid DNA. Plasmid cleavage studies carried out with a non-redoxable Zn(2+) complex (2) supported the role of the redox activity of copper in 1. The complex 1 showed remarkable antiproliferative activity against cancer cell lines, viz., cervical (HeLa, SiHa, CaSki), breast (MCF-7), liver (HepG2) and lung (H1299). A considerable lowering was observed in the IC(50) values of HPV-infected (viz., HeLa, SiHa, CaSki) vs. non-HPV-infected cell lines (MCF-7, HepG2, H1299). Antiproliferative activity of 1 was found to be much higher than the carboplatin when treated with the same cell lines. Incubation of the cells with 1 results in granular structures only with the HPV-infected cells and not with others as studied by phase contrast and fluorescence microscopy. The lower IC(50) value observed in case of 1 with HPV-infected cell lines may be correlated with the involvement of HPV oncoprotein. The role of HPV has been further augmented by transfecting the MCF-7 cells (originally not possessing HPV copy) with e6 oncoprotein cDNA. To our knowledge this is the first copper complex that causes cell death by interacting with HPV oncoprotein followed by exhibition of remarkable antiproliferative activity.

The compounds [H,NCMe,CH,OH] [VO,L]{H,L = [l + 1 J Schiff base derived from salicylaldehyde (or substituted derivatives) and 2-amino-2-methylpropan-1-01) have been synthesized in good yields by reaction of the Schiff base (formed in situ) and a further equivalent of the amino alcohol with [VO(acac),] (Hacac = acetylacetone). The structures of three of the complexes have been solved by single-crystal X-ray studies. All the compounds were also characterized by UV/VlS, FTIR and N M R spectroscopy and by cyclic voltammetry. The three structurally characterized mononuclear complexes contain the cis-dioxovanadium(v) moiety and exhibit distorted square-pyramidal geometry at vanadium which is displaced from the equatorial plane by ~0 . 5 p\. The crystal and molecular structures of these compounds showed extensive hydrogen bonding between the anionic portion of the complexes and the counter-cations of the amino alcohol which resulted in some unusual metric features of interest to the binding of vanadium in biological systems. Two of the compounds showed

Hydrogels have been used in the literature in tissue engineering, in drug delivery, and as enzyme biomimics. Herein, we report the synthesis of a functional biomaterial using BSA as scaffold and epichlorohydrin as cross-linker. The hydrogels reported in this paper were shown to exhibit tunable pore size as a function of BSA concentration by scanning electron microscopy (SEM) and, therefore, are well suited to encapsulate drug molecules for delivery applications. These are injectable, shear thinning, self-healing, and has the ability to withstand a physical weight of ∼300 times of its own. In trypsin medium, the gel is degraded by 50% in 36 h supporting that these are biodegradable. The loading of Dox by the gel was confirmed by the emission of red fluorescence and also by filling the pores by fibrillar structures as demonstrated by SEM. The controlled release of Dox occurs over 5 days to an extent of 37 ± 2%, 26 ± 0.5%, and 21 ± 1.5% in PBS at pH 5.5, 6.8, and 7.4 respectively. Since these hydrogels are made of BSA as matrix, their biocompatibility was proven by MCF-7, HeLa, and MDA-MB-231 cells wherein 95 ± 5% of cells are viable when treated with unloaded hydrogel. However, the Dox loaded hydrogel results in 70–80% of killing in the case of all three cancer cells. Fluorescence microscopy and FACS studies support controlled and time dependent release of Dox in MCF-7 cells for 24 h where the drug goes into cytoplasm initially and then into nucleus. The cell cycle analysis carried out using MCF-7 cells clearly showed that the cell death is due to apoptosis, and this is by arresting the G2/M phase as a function of time. All of the data supports the utility of the synthesized BSA hydrogel as a biomaterial that will find application in controlled drug delivery.

A fluorescence turn-on receptor based on triazole linked calix[4]arene (L) for selective recognition of Zn(2+) in aqueous-methanolic HEPES buffer has been developed and showed its utility for sensing Zn(2+) in blood serum milieu.

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