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A new highly selective fluorescent chemosensor for Nickel ion was developed based on pyrene-conjugated pyridine. The ratiometric sensing of Nickel ions by the chemosensor in solution is by the formation of a monomer-excimer emissions. It’s a reversible sensor and has a detection limit up to micro molar level. All the findings were supported by the DFT studies. In addition, ratiometric fluorescent changes upon the addition of nickel ions, is also applied in cell imaging.

A new highly selective fluorescent chemosensor for Ag + was developed based on an imidazole conjugated quinolone bearing a thiol group ( IQT ). The Chemosensor serves as fluorescence quencher for Ag + in solution in the presence of other competing metal ions. Further, the in situ formed IQT -Ag + complex is utilized as a reversible sensor for the amino acid, Proline with high selectivity over other amino acids by a fluorescence enhancement mechanism as relay recognition process. The practical applications for sensor IQT is also demonstrated by the complete removal of Ag + ions from the environmental water samples via electrochemical desalination techniques and its bioimaging in cellular micro-organisms.

A new series of bivalent Ni(II), Cu(II) and Zn(II) metal complexes containing Schiff base ligand [H-emk-sadtc] [(E)-allyl 2-(butan-2-ylidene) hydrazine carbodithioate)] were synthesized and characterized by different spectroscopic techniques. The molecular structure of the ligand and its complexes 1 [(E)-allyl 2-(butan-2-ylidene) hydrazine carbodithioato nickel(II)], complex 2 [(E)-allyl 2-(butan-2-ylidene) hydrazine carbodithioato copper(II)], complex 3 [(E)-allyl 2-(butan-2-ylidene) hydrazine carbodithioato zinc(II)] were confirmed by single crystal X-ray crystallography. XRD data of the complexes had revealed a distorted square planar geometry around the metal ion, satisfied by N2S2 fashion. Density functional calculations of all the compounds in gas phase were performed by using DFT (B3LYP) with 6-311G basis set. The calculated FT-IR and structural data are in good agreement with the experimental results and confirmed by the experimental one. The interactions of calf thymus (CT) DNA and bovine serum albumin (BSA) with complexes 1–3 were explored by emission spectra. Catecholase and phosphatase-like activities of all the complexes were also investigated. An in vitro cytotoxicity study of the complexes had shown significant activity against human cervical cancer cell line (HeLa) with the best results of complex 2, which was found to be more toxic to cancer cells with a few micromolar concentrations, as the IC50 value, but significantly less toxic to normal cell lines. Additionally, the cell death analysis was carried out by AO/EB and DAPI staining methods.

A series of hybrid thiosemicarbazone derivatives (H2L1–3) were synthesized by the reactions of diacetyl-2-(4-methyl-3-thiosemicarbazone) with hydrazine derivatives such as 2-hydrazinoquinoline, 2-hydrazinobenzothiazole and 6-hydrazinonicotinic acid arm. The resulting hybrid diacetyl-2-(4-methyl-3-thiosemicarbazonato-hydrazine derivatives were successfully employed as tetradentate ligands to react with [RuHClCO(PPh3)3]. The reactions have led to the binuclear organo-ruthenium(II) complexes of the core type [Ru2(Ln)2(CO)2(μ-S)2], (n = 1–3) in which the ruthenium(II) ion bridged by sulphur atoms (μ-S)2. In the new complexes, the ligand charge and stoichiometry proportions could be controlled by the addition of base. All the compounds have been characterized by IR, UV–vis, ESI-MS, (1H, 13C) NMR spectra and elemental analyses. The crystal structure of complexes 1, 2 has been determined by X-ray crystallography, which confirmed the coordination mode of the ligands and revealed a distorted octahedral geometry around the ruthenium ion. Natural bond orbital calculations of complexes 1 and 2 showed that the majority of the electron density of donors tends to the ruthenium ion, since the calculated Mulliken charge for the ruthenium ion is much lesser than the formal value. The binding mode of these complexes with biomolecules such as calf thymus DNA (CT-DNA) and bovine serum albumin (BSA) protein have been investigated by diverse spectrophotometric methods and the results revealed an intercalative mode of interaction. Furthermore, the bio-catalytic efficiencies such as catecholase and phosphatase like activities of ruthenium complexes exhibited high rate (kcat) constant. Furthermore, the complexes (1–3) displayed more cytotoxicity against anticancer cell lines such as MCF-7 (breast), A549 (lung), and HepG2 (liver) than normal Vero cell line. The less cytotoxic activity towards normal cell lines showed that they affect only cancer cell lines. The antiproliferative efficacy of complexes (1–3) has also been analyzed using morphological staining properties (AO/EB, DAPI) by fluorescence microscopy visualization.

New palladium(II) complexes {[Pd(L)(PPh 3 )] ( 2 ) and [Pd(L)(AsPh 3 )] ( 3 )} have been synthesized by using 4-hydoxy benzoic acid (5-chloro-2-hydroxy-benzylidene)-hydrazide (H 2 L) ( 1 ) ligand. The structure of the ligand (H 2 L) ( 1) , and complexes ( 2 and 3) were confirmed by using analytical, spectral and single crystal X-ray diffraction techniques. The structure of complexes ( 2 and 3 ) revealed a square planar geometry around the Pd ion in which the hydrazone is coordinated through ONO atoms. The interaction of the compounds with calf thymus DNA (CT-DNA) was investigated by absorption, emission titration, electrochemical and viscosity methods, indicating that the ligand and the complexes interacted with CT-DNA through intercalation. The good interaction of the ligand and the Pd(II) complexes with bovine serum albumin (BSA) protein was confirmed by UV–visible and fluorescence spectroscopic studies. The better free radical scavenging ability of Pd(II) complexes was evaluated by in vitro antioxidant assays involving DPPH radical, hydroxyl radical and nitric oxide radical. Furthermore, in vitro cytotoxicity studies of 2 and 3 showed higher activity with lower IC 50 values even at low concentrations.

A simple hydroxyl-substituted triphenyl-imidazole based receptor (HTPI) which selectively detects Cu2+ ion by colorimetric and fluorimetric methods was developed. HTPI detects the Cu2+ ions with the absorption enhancement and fluorescence quenching by the possible ligand to metal charge transfer (LMCT) and the chelation-enhanced quenching (CHEQ) approaches, respectively. HTPI showed high selectivity and sensitivity for Cu2+ ions detection over other interfering and competing metal ions. Interestingly, HTPI detects Cu2+ ion (LOD) at nanomolar concentrations (19 × 10−9 M (UV–vis) & 27 × 10−9 M (fluorescence), respectively), which is lower than the permissible level of Cu2+ ion reported by World Health Organization (WHO). Furthermore, HTPI was applied to the molecular logic gate function by using chemical inputs, and Cu2+ ion was potentially removed (95%) via Capacitive Deionization technique.

A quantitative mercuric detection is very important in the environmental and biological systems. In this paper, we report a novel bis-rhodanine derived fluorescent chemosensor for recognition of Hg2+ ion in DMSO-H2O (1:1) medium. The ‘turn-on’ fluorescence response was exhibited specifically toward Hg2+ over other metal ions by receptor R2 at 410 nm, which could be ascribed to the restriction of photo-induced electron transfer (PET) process and chelation-enhanced fluorescence (CHEF) effect upon the complexation with mercury ions. The complexing stoichiometry of receptor R2 to Hg2+ was estimated to be 1:1 according to Job’s plot experiments. The limit of detection was calculated to be 7.33 × 10−7 M based on the concentration dependent emission changes with good association constant of 8.97 × 104 M−1. As a result, we express that receptor R2 is a promising candidate for Hg2+ recognition without any significant interference of other co-existing cations. The receptor R2 was successfully applied to molecular logic and keypad lock applications and real water samples to determine its potential applications.

There is a continuous finding of suitable metal complexes for biomedical and biological applications since the discovery of cisplatin. Two biologically active complexes (2 and 3) are synthesized by using 2-chloro-benzoic acid (3,5-dichloro-2-hydroxy-benzylidene)-hydrazide (1) ligand. The ligand (1) and complexes (2 & 3) are characterized by various spectroscopic tools. The molecular structures of (1) and (3) are confirmed via., XRD data. The spectroscopic and XRD data reveals that the ligand coordinates to palladium through ONO chelation and the geometry of the complexes is distorted square planar. The in vitro interaction of the synthesized compounds with calf-thymus DNA (CT-DNA) are analysed through different experiments which shows the intercalation mode of binding. Further, the interaction studies of the compounds with bovine serum albumin protein (BSA) show that, the compounds binds strongly with BSA. Also, antioxidant studies have been carried out with the compounds. Finally, MTT assay reveals that, the Pd(II) complexes displayed significant activity against HeLa and MCF-7 cancer cell lines.

Transition metal complexes of acetophenone-S-allyldithiocarbazate [H-(Ap-sadtc)] of the general formula [M-(Ap-sadtc)2] (Ni2+, Cu2+, Zn2+) (1–3) were synthesized and characterized by elemental analysis, UV–Vis, FT-IR, 1H NMR, 13C NMR and mass spectroscopy. The molecular structures of the ligand and its complexes 1–3 were confirmed by both theoretical as well as experimental methods. The interactions of the complexes with biomolecules, such as calf thymus DNA (CT-DNA) and bovine serum albumin (BSA), were explored using absorption and emission spectral techniques. All the complexes synthesized were found to be most promising due to their large binding affinity towards different bio-macromolecules and higher Kcat values in catechol oxidation (3,5-DTBC)/phosphate hydrolysis (4-NPP) reactions. The in vitro anticancer activities using MTT and a morphological staining assay indicate that the complexes are active against the (Hela) cervical cancer cell line, which is consistent with our above mentioned hypothesis.

New nickel(II) complexes containing 4-chromone N (4)-substituted thiosemicarbazone ligands of the type [Ni(L 1–3 ) 2 ](NO 3 ) 2 ·H 2 O ( 1 – 3 ) [4-chromone-4-methylthiosemicarbazone (L 1 ), 4-chromone-4-phenylthiosemicarbazone (L 2 ), 4-chromone-4-cyclohexylthiosemicarbazone (L 3 )] were synthesized and characterized by analytical and various spectroscopic techniques. The single crystal X-ray diffraction study of the complex 1 revealed a distorted octahedral geometry around the metal center. The new complexes were subjected to biological investigations such as DNA/protein interaction studies and in vitro cytotoxic study against human breast cancer cell line (MCF-7). The DNA binding by fluorescence spectral study showed that the complexes bind to DNA via intercalation binding mode. Protein binding studies using fluorescence spectroscopy showed that the new complexes could bind strongly with bovine serum albumin (BSA). The complexes have good anticancer activity against MCF-7 cancer cell line due to the terminal substituted thiosemicarbazones.

A naphthalene pyridine Schiff base 1 as a fluorescent chemosensor was developed for the detection of Fe 2+ ions in CH 3 CN–H 2 O solution. Its binding properties toward various other heavy and transition metal ions including Fe 3+ ions were examined. The sensor showed high selectivity and sensitivity towards Fe 2+ ions in aqueous media with the lower detection limit of 1.5 × 10 −7 M. The fluorescence “turn-on” recognition process follows the ICT process and C N isomerisation. In addition, determination of Fe 2+ in a variety of samples were analyzed which includes commercially available tablets, tomato juice, dark chocolate and tap water.

Binol-pyrene conjugate (BPC), as fluorescent probe was synthesized by multi-step synthetic strategies. BPC acts as a single sensor for dual analyte detection by a turn “on-off” mechanism for Ag+ and CO32- ions. In the emission spectra, the monomer peaks of BPC were drastically quenched by the addition of Ag+ and CO32- ions, due to the reverse photo-induced electron transfer (PET) process, excited-state deactivation via vibration and rotation of binaphthyl ring and the heavy atom effect responsible for the spin forbidden process. The probe BPC is highly selective and sensitive to Ag+ and CO32- ions even in the presence of various interfering cations and anions at the physiological pH. The similar sensing strategy of BPC for Ag+ and CO32- ions were further applied into the living cells, and their limit of detection (LOD) downs to 1.2 × 10-7 M and 14 × 10-6 M, respectively, which are close to the World Health Organization (WHO) drinking water standards. Furthermore, the binding interaction between the probe BPC with Ag+ and CO32- ions and dynamic mode of quenching are evidenced by Stern-Volmer plots, quantum yields, NMR and DFT analysis.

A highly responsible Fe3+, azine chemosensor (EBHMM) was successfully designed and synthesized. The structure of the synthesized azine was confirmed by FT-IR, UV–Vis, 1H and 13C{1H} NMR spectroscopic techniques and high resolution mass spectrometry. The azine shows sensitive and selective fluorescence “turn-off” towards Fe3+ ion over other metal ions in 1:1 DMF-H2O (5 μM, pH = 7.4) solution. The fluorescence quenching on the addition of Fe3+ ion at various pH clearly indicate that the azine can be used for the quantitative determination of Fe3+. The binding of Fe3+ with chemosensor was analyzed by confirming the formation of metal-ligand complex using HRMS-ESI spectrometry. The binding stoichiometry (1:1) was calculated using Stern-Volmer method and the binding constant 1.0034 M-1 was calculated using Benesi-Hildebrand plot. The exact binding sites of the chemosensor with Fe3+ ion is theoretically explained with Fukui Function using DFT study in B3LYP function with B3LYP/6-311++G (d,p) level of basis set. The “turn-off” fluorescence through photo induced electron transfer (PET) process is discussed and confirmed with the results of Fukui Function and Frontier molecular orbital analysis.

Quinoline based fluorescent probes were formulated for the precise detection of cerium ions. Probes 1 and 2 detect Ce3+ ion as opposed to other metal ions through fluorescence in HEPES buffered CH3CN-H2O (1:1, (v/v) HEPES =50 mM, pH = 7.4) solution. The Ce3+ ion recognition process follows the π to π* transitions and intramolecular charge transfer (ICT) mechanisms. The LOD (Limit Of Detection) of probes 1 and 2 for sensing Ce3+ ion were found to be 1.60 × 10−9 M and 0.17 × 10−9 M, respectively. These probes are further utilized to detect Ce3+ ion by electrochemical studies. The practical applications of the probes are tested for varied biological applications.

A new simple pyrene based schiff base chemosensor 1 (nicotinic acid pyren-1-ylmethylene-hydrazide) has been constructed and is prepared from 1-pyrenecarboxaldehyde and nicotinic hydrazide. Notably, the chemosensor 1 exhibited remarkable colour changes while in the presence of trivalent metal ions like Bi3+ & Al3+ ion in DMSO-H2O, (1:1 v/v, HEPES = 50 mM, pH = 7.4). The UV–Vis spectral investigation of chemosensor 1 showed that the maximum absorption peak appeared at 378 nm. In emission studies, chemosensor 1 develops weak fluorescence, while upon the addition of Bi3+ and Al3+ ions, it exhibits an enhancement of fluorescence intensity. Nevertheless, rest of metal ions have no changes in the emission spectra. The association constant of chemosensor 1 for binding to Bi3+ & Al3+ system had a value of 1.27 × 104 M−1 and 1.53 × 104 M−1. The detection limits were 0.12 µM for Bi3+ and 0.17 µM for Al3+ respectively. The overall results reveal that chemosensor 1 can act as a dual-channel, highly selective, and sensitive probe for Bi3+ and Al3+ ions. Moreover, the fluorescence imaging of chemosensor 1 was applied in RAW 264.7 cell line and cytotoxicity assay prove that this chemosensor 1 is non-toxic as well as highly biocompatible.

An imidazole derivative (probe L1) bearing a thiophene group was developed as an ON-OFF fluorescent chemosensor for palladium ions. The UV–vis absorption and fluorescence spectral behavior of probe L1 towards various cations were investigated in HEPES buffer aqueous solution. The absorbance intensity of probe L1 considerably enhanced whereas the fluorescence emission intensity was quenched in the presence of Pd2+ ions, while the presence of other metal ions had no notable interference. The stoichiometry of the complex was determined using Job’s plot and a plausible recognition mechanism of probe L1 and Pd2+ is proposed. Density Functional Theory (DFT) calculations were used to study the electronic properties and to optimize the structure on the selectivity of Pd2+ ions and are correlated with the experimental results. The intracellular Pd2+ ion detection in living cells was performed using probe L1 on brine shrimp nauplii (Artemia salina) up to 20 μg/mL.

A simple anthracene based chalcone as a fluorescent chemosensor, capable of detecting Pb2+ in aqueous media, has been synthesized by the reaction between benzaldehyde and 9-acetyl anthracene. The Pb2+ recognition process follows a photo-induced electron transfer mechanism and is scarcely influenced by other coexisting metal ions. Determination of lead in a variety of water samples was performed.

A simple dimeric binol-based fluorescent chemosensor S-1, capable of detecting Hg2+ in aqueous media is designed and synthesized. The Hg2+ recognition processes follow a photo induced electron transfer (PET) mechanism and are scarcely influenced by other coexisting metal ions. In addition, determination of mercury in waste water samples was also analysed.

A simple anthracene based chalcone as a fluorescent chemosensor 1, capable of detecting Pb2+ in aqueous media, has been synthesized by the reaction between pyridine 2-carboxaldehyde and 9-acetyl anthracene. The Pb2+ recognition processes follows a photo induced electron transfer (PET) mechanism and are scarcely influenced by other coexisting metal ions. In addition, determination of lead in a variety of samples was also determined.

As a contribution to the development of new ruthenium complexes with pharmacologically interesting properties, two new mononuclear ruthenium(II) complexes of the general formula [Ru(H-Nap-sbdtc)Cl(CO)(EPh3)2] (1 & 2) [H-(Nap-sbdtc) = 2-hydroxy-1-naphthaldehyde-S-benzyl-dithiocarbazate; E = P or As] were synthesized. The new ruthenium(II) carbonyl complexes are remarkably stable and were obtained in good yields. Their identities have been established by satisfactory elemental analyses and various spectroscopic techniques (IR, UV/visible, (1H, 13C, and 31P) NMR, and ESI-MS). For a better definition, the molecular structure of complexes 1 and 2 has been determined by X-ray crystallography, which confirms the coordination mode of the ligand and reveals a distorted octahedral geometry around the ruthenium ion. The molecular structure of complexes 1 and 2 has been optimized by DFT calculations. The binding affinity and binding mode of the ligand and their ruthenium(II) complexes toward calf thymus CT-DNA were determined by the emission spectral method, the fluorescent indicator displacement (FID) assay and viscosity measurements. Further, the interactions of the ligand and their complexes 1 and 2 with bovine serum albumin (BSA) were investigated using UV-Vis and fluorescence spectroscopic methods. Absorption and emission spectral studies indicate that complexes 1 and 2 interact with CT-DNA and BSA protein more strongly than their parent ligand. In addition, the interactions of the complexes with DNA/BSA were followed by electrophoretic mobility spectrometry studies and the results show that these complexes exhibited good cleavage properties. In vitro anticancer activity has been scrutinized by the MTT assay, acridine orange/ethidium bromide (AO/EB) and diamidino-2-phenylindole (DAPI) staining against the human cervical cancer (HeLa) cell line.

With the aim of assessing whether transition metal complexes might be utilized as efficient biocatalysts and biological drugs, new monofunctional nickel(II) and copper(II) complexes of types NiL (1) and CuL (2) [H2L ¼ N-(N0 ,N0-diethylaminothiocarbonyl)benzimidoyl chloride-2-aminoacetophenone-N-methylthiosemicarbazone] were synthesized. The compounds are remarkably stable and were obtained in good yields. Structural elucidation was carried out thoroughly in solid and solution-states by elemental analysis and various spectroscopy techniques (IR, UV-vis, 1H NMR, and EPR) as well as ESI mass spectrometry. The molecular structure of the compounds was investigated by single-crystal X-ray diffraction. The analyses showed tetradentate coordination of the ligand in nickel(II) and copper(II) complexes, in which the metal atom exhibits a square planar geometry with N2S2 in a donor fashion. Structural optimization, HOMO–LUMO energy calculations and Natural Bond Orbital (NBO) analysis of H2L and its complexes (1 and 2) were investigated by Density Functional Theory (DFT). The trend in binding affinities of the compounds with biomolecules, such as calf thymus DNA (CT-DNA) and bovine serum albumin (BSA) protein, were investigated by different spectrophotometric methods, which revealed an intercalative mode of interaction. Furthermore, enzyme kinetic studies reflected that the square planar complexes (1 and 2) are also effective in mimicking catecholase (3,5-DTBC) and phosphatase (4-NPP) activities over the parent H2L. The high kcat values suggested that the selected compounds displayed a high rate of catalytic efficiency. In vitro cytotoxicity of the complexes on human skin cancer melanoma (A375), human cervical cancer (HeLa) and human hepatocellular carcinoma (Hep3B) cancer cell lines demonstrated that the complexes had a broad-spectrum of anti-cancer activity with low IC50 values. The morphological assessment data obtained by acridine orange/ethidium bromide (AO/EB) and diamidino-2-phenylindole (DAPI) staining revealed that complex 2 induces apoptosis much more effectively than 1.

A new two dipicolyl amine (DPA) dangled 2,5-diphenyl-1,3,4-oxadiazole derivatized sensor L has been designed and synthesized. Sensor L displays excited state intramolecular proton transfer (ESIPT) properties in buffered water solution (HEPES 10 mM, pH = 7.4). L shows highly selective and ratiometric fluorescence responses to Zn2+ in a 1 : 2 binding ratio. Fluorescence spectra and 1H NMR studies demonstrate that L binds Zn2+ ions through its amide form, which promoted the ESIPT emission enhancement. The in situ generated L–2Zn2+ complex can serve as a relay recognition sensor toward PPi and S2− via further complexation and Zn2+ sequestering processes respectively. Thus, multi-analyte and relay recognition of L through modulating ESIPT has been achieved.

A quinoline benzimidazole-conjugate (QBC) has been synthesized for the highly selective detection of Zn(II) both by colorimetry and fluorimetry. Probe QBC senses Zn2+ over other cations as fluorescence ‘off–on’ behaviour in HEPES-buffered CH3CN–H2O (1 : 1, v/v, pH = 7.0) solution. A possible mechanism is proposed based on the inhibition of PET and intramolecular restricted torsional rotation through the C–C single bond between the quinoline benzimidazole-conjugate. The Chemosensor is utilized to detect Zn2+ in much real sample analysis.

New ruthenium(II) complexes with formulae [RuCl(CO)(PPh3)2L1] and [RuCl(CO)(PPh3)2L2] (L1 = S-allyl-4-methoxy benzylidene hydrazine carbodithioate, L2 = S-allyl-1-naphthylidene hydrazine carbodithioate) have been synthesized and characterized by elemental analysis, Fourier transform infrared (FTIR), nuclear magnetic resonance (NMR), UV-Vis, electrospray ionization (ESI)-mass spectral studies. Both the Schiff base ligands are coordinated to ruthenium through azomethine nitrogen (C=N) and thiolato sulfur donor atoms in the thiolate form. On the basis of spectral data obtained, an octahedral structure has been assigned to all the new complexes, satisfied by coordination of donor atoms N and S. The stability of complexes in solution was determined by molar conductivity measurements. The interaction of the two complexes with calf thymus (CT) DNA was investigated by fluorescence spectroscopic and viscometric methods. Bovine serum albumin (BSA) protein was examined by fluorescence spectroscopic methods. These techniques indicate that the two metal complexes bind to DNA via intercalation mode and BSA bind with static interaction. Catecholase and phosphatase like activities promoted by these two complexes under physiological conditions have been studied. In vitro anticancer activities have been demonstrated by 3,4,5-dimethylthiazolyl-2-2,5-diphenyltetrazolium bromide (MTT) assay, acridine orange/ethidium bromide (AO/EB) and diamidino-2-phenylindole (DAPI) staining against HeLa cancer cell line.

A novel auxillary chiral dimeric binol has been designed, synthesized, and used to enantioselectively recognize 1,2-amino alcohols through the three point of interactions, the reversible imine bond, resonance assisted hydrogen bonding and the hydrogen bonding by the additional chiral moiety introduced at the receptor. The enantioselectivities were comparable to those of the previous reported receptors.

New Ru(III) isothiosemicarbazone complexes [RuCl(EPh3)L(1-4)] (E=P or As) were obtained from the reactions between [RuCl3(EPh3)3] and bis(salicylaldehyde)-S-methylisothiosemicarbazone (H2L(1-3))/bis(2-hydroxy-naphthaldehyde)-S-methylisothiosemicarbazone (H2L(4)) ligands. The new complexes were characterized by using elemental analyses and various spectral (UV-Vis, IR, (1)H NMR, FAB-Mass and EPR) methods. The redox properties of the complexes were studied by using cyclic voltammetric method. The new complexes were subjected to various biological investigations such as antioxidant assays involving DPPH radical, hydroxyl radical, nitric oxide radical and hydrogen peroxide, DNA/protein interaction studies and in vitro cytotoxic studies against human breast cancer cell line (MCF-7). New complexes showed excellent free radicals scavenging ability and could bind with DNA via intercalation. Protein binding studies using fluorescence spectroscopy showed that the new complexes could bind strongly with bovine serum albumin (BSA). Photo cleavage experiments using DNA of E-coli bacterium exhibited the DNA cleavage ability of the complexes. Further, the in vitro anticancer activity studies on the new complexes against MCF-7 cell line exhibited the ability of Ru(III) isothiosemicarbazone complexes to suppress the development of malignant neoplastic disease cells.

Cobalt(III) complexes containing pyridoxal N(4)-substituted thiosemicarbazone ligands with the composition [Co(HL1−2·Cl)(HL1−2·H2O)] (1–2) have been synthesized from the reaction of [CoCl2(PPh3)2] and pyridoxal N-methyl-thiosemicarbazone hydrochloride (H3L1·Cl)/pyridoxal N-phenyl-thiosemicarbazone hydrochloride (H3L2·Cl). The richness of the coordination chemistry of this ligand is highlighted by the modulation of its charge from neutral (H3L·Cl) (L) to dianionic (HL·Cl) (L2−) and monoanionic forms (HL·H2O) (L−) and coordinated as tridentate binegative mode around cobalt(III) ion by forming neutral complex. The new complexes were characterized by various analytical and spectroscopic techniques (IR, electronic, 1H NMR and ESI-Mass). The X-ray crystal structure of the complex 2, demonstrated distorted octahedral coordination geometry around the metal centre. Further, the investigation of effect of substitution (CH3 or C6H5) on terminal N(4)-nitrogen of thiosemicarbazone exhibited its influence on the potential binding and cleavage ability with DNA, BSA binding, free radical scavenging and cytotoxicity.

A simple chalcone-based fluorescent chemosensor 1, capable of detecting Fe3+ in aqueous media, has been designed and synthesized by the condensation of 3-formyl-2-hydroxyquinoline and acetophenone. The Fe3+ recognition processes are shown to be barely influenced by other coexisting metal ions, and are found to be reversible with EDTA. Moreover, the sensor is applied in the Fe3+ removal process from environmental water samples by using a membrane separation method.

A new pyrene pyridine conjugate (PPC) has been developed as a selective fluorescent sensor for Ag+ ion. Probe PPC exhibits high selectivity and sensitivity toward Ag+ as fluorescence ‘on–off’ behaviour in HEPES-buffered DMSO–H2O (1 : 1, (v/v) HEPES = 50 mM, pH = 7.4) solution with a detection limit of 0.29 × 10−8 M−1. The turn-off fluorescence sensing of the Ag+ ion occurs through dual pathways, i.e. changes and alternations in the photophysical properties. The binding of Ag+ ion prevents excimer formation and also induces intramolecular photoinduced electron transfer (PET) from the pyridine–Ag+ ion bound receptor to pyrene because of structural rigidification, which quenches excimer and monomer emissions with a butterfly-like skeleton.

Four binol based pyrrole carboxamide chiral receptors has been synthesized and effectively used as a Chirality Conversion Reagent (CCR) for underivatized amino acids. Three points of interactions take place for the conversion process. They are the reversible imine formation, the internal resonance assisted Hydrogen Bonding (RAHB) and the additional hydrogen bonds between the amino acids and the heterocylic moiety of the pendant groups. The conversion efficiency of all the receptors was found to be comparable with those of the receptors reported earlier.

The synthesis, structure and biological studies of cobalt(III) complexes supported by NNS-tridentate ligands are reported. Reactions of 2-acetylpyridine N-substituted thiosemicarbazone (HL(1-3)) with [CoCl2(PPh3)2] resulted [Co(L(1-3))2]Cl (1-3) which were characterized by elemental analysis and various spectral studies. The molecular structure of the complex 1 has been determined by single crystal X-ray diffraction studies. In vitro DNA binding studies of complexes 1-3 carried out by fluorescence studies and the results revealed the binding of complexes to DNA via intercalation. The binding constant (Kb) values of complexes 1-3 from fluorescence experiments showed that the complex 3 has greater binding propensity for DNA. The DNA cleavage activity of the complexes 1 and 3 were ascertained by gel electrophoresis assay which revealed that the complexes are good DNA cleavage agents. Further, the interactions of the complexes with bovine serum albumin (BSA) were also investigated using fluorescence spectroscopic method, which showed that the complexes 1-3 could bind strongly with BSA. The antioxidant property of the complexes was evaluated to test their free-radical scavenging ability. Furthermore, in vitro cytotoxicity of the complexes against MCF-7 and A431 cell lines was assayed which showed higher activity and efficiently vanished the cancer cells even at low concentrations.

A fluorescence-enhanced naphthalene based chemodosimeter 1 for Hg2+ was developed via Hg2+-promoted irreversible desulfurization reaction. Spectroscopic results reveal that chemodosimeter 1 exhibits high selectivity for Hg2+ in comparison to common interfering metal ions.

Three representative BINOL derivatives were examined for their chiral recognitions with D- and L-t-Boc-amino acid anions: an open system 1, which bears two urea groups and two pyrene groups; a closed ring system 2, which bears two urea groups with a closed ring system; and a dimeric system 3, which bears two benzylic amine groups and two pyrene groups. Dimeric system 3 displayed a ΔI(D)/ΔI(L) of 12.95 for t-Boc-alanine.

To realize highly selective relay recognition of Cu2+ and sulfide ions, a simple benzimidazole-based fluorescent chemosensor (1) was designed and synthesized. Sensor 1 displays rapid, highly selective and sensitive recognition to Cu2+ in 100% water solution at pH 6.0. The in situ generated 1-Cu2+ complex solution exhibit a fast response and high selectivity toward sulfide anion via Cu2+ displacement approach. The detection limits of sensor 1 to Cu2+ and 1-Cu2+ complex to sulfide anion were estimated to be 3.5 × 10−7 M and 1.35 × 10−6 M, respectively. Proof-of-concept experiment results demonstrate that sensor 1 has potential utilities for Cu2+ and sulfide ion concentration evaluation in real water samples. This successive recognition feature of sensor 1 makes it has a potential utility for Cu2+ and sulfide anion detection in water.

The chiral ketone (S)-3 shows high kinetic enantioselectivities toward the L form for general underivatized amino acids with hydrophobic side chains and a high thermodynamic enantioselectivity toward the D form for cysteine with its -SH polar side chain when used as an extractant in enantioselective liquid-liquid extractions in the presence of Aliquat 336. Consecutive extractions by imine formation and hydrolysis increase the enantiopurity of the amino acid, as both of these reactions are L-form-selective.

A new benzimidazole-based quinazoline derivative (1) has been designed and synthesized as a fluorescent probe. Probe 1 exhibits high selectivity and sensitivity to Cu2+ as fluorescence ‘on–off’ behavior in HEPES-buffered CH3OH/H2O (1:1, v/v, pH = 7.0) solution. The in situ formed 1-Cu2+ complex is further utilized to sense the cyanide ions with high selectivity and fluorescence enhancement performance.

Two new palladium(II) complexes of 4-hydoxy-benzoic acid (5-bromo-2-hydroxy-benzylidene)-hydrazide (H2L) (1) with triphenylphosphine and triphenylarsine as coligand have been synthesized and characterized by the aid of various spectral techniques. The structure of the ligand and complexes was confirmed by single crystal X-ray diffraction studies. The hydrazone ligand acts as a tridendate ligand with ONO as the donor sites and is preferably found in the enol form in all the complexes. The structural analysis of 2 and 3 confirms the square planar geometry of the two complexes. The DNA binding of these complexes and ligand calf thymus DNA (CT-DNA) was investigated by using various methods, which revealed that the compounds interacted with CT-DNA through intercalation. Binding properties of the free ligand and its complexes with bovine serum albumin (BSA) protein have been investigated using UV-visible and fluorescence spectroscopic methods which indicated the stronger binding nature of the palladium complexes to BSA than the free hydrazone ligand. In addition, concentration dependent free radical scavenging potential of all the synthesized compounds (1-3) was also carried out under in vitro conditions. Further, the in vitro cytotoxicity of the compounds was examined on a HeLa and MCF-7 cell lines, which revealed that complex 2 exhibited a superior cytotoxicity than complex 3 and ligand 1.

A novel reduced graphene oxide ( rGO) decorated organic binol based receptor ( (S)-1) has been designed and synthesized. The resulting nanocomposite ( rGO(S)-1) material was then utilized as a selective fluorescent chemosensor for Ag+ ion in aqueous media at physiological pH. In addition, the nanocomposite showed no crossreaction with any of the potential interfering metal ions. The reduced graphene oxide-organic nanocomposite was characterized using various spectroscopic, microscopic and analytical studies.

2-Hydroxy-6-(1-(3-phenylurylphenyl)ethoxy)-benzaldehyde (2) has been synthesized in racemic form from 1,3-Dihydroxybenzene via formylation and reaction with 3-phenyluryl-methylbenzylbromide. The optically pure form of 2 was separated by normal silica column chromatography from the imine diastreomer which was obtained by the reaction of racemic mixture of 2 with optically pure leucinol. The absolute configuration of the separated enantiomer of 2 was decided from the energy calculation of the corresponding imine diastereomers. The activity of 2 as a chirality conversion reagent (CCR) for amino acids was determined by 1 H NMR analysis. The efficiency of 2 is not better than the previous CCRs based on binaththol. Compound 2, however, has lower molecular weight compared to other CCRs. This work demonstrates that asymmetric carbon can control the selectivity of amino acids.

An easy and convenient synthetic route to (S)-2-hydroxy-2'-(3-phenyluryl-benzyl)-1,1'-binaphthyl-3-carboxaldehyde (1), capable of recognizing tryptophan by fluorescence has been developed. The binol carboxaldehyde 1 exhibited a high selectivity to L-tryptophan over other examined L--amino acids such as alanine, phenylalanine, glutamine, arginine, lysine, serine, threonine, aspartat, valine, histidine and cysteine, with a fluorescence "turn-on" signal. In addition, 1 displayed chiral discrimination with good enantioselectivity toward L-tryptophan over D-tryptophan through different fluorescence enhancement factors.

recognition processes are observed to be barelyinterfered by other coexisting metal ions. Key Words : Chemosensor, Colorimetric, Fluorescent, Rhodamine B, RecognitionIntroduction The development of optical molecular or polymeric systemscapable of sensing various biologically and/or environ-mentally important cations, as chemosensors, has generatedsignificant interest in recent years. At the present time, UV-vis and fluorescence spectroscopy are the most frequentlyused modes of detection of these sensors, due to their highsensitivity and easy operability. The emerging new conceptof “single sensor for multiple analytes’ for chemosensordesign is the analysis of two or more analytes by onereceptor utilizing a single detection method or an array ofdetection method.

E-mail: rajunandha@gmail.comReceived January 29, 2011, Accepted February 15, 2011Novel binol-based uryl and guanidinium receptors having higher ring conjugation at the periphery of thehydrogen bonding donor sites have been synthesized and utilized to study the enantioselective recognition of1,2-aminoalcohols and chirality conversion of natural amino acids via imine bond formation. There is aremarkable decrease in the stereoselectivites as the conjugation increases at the periphery of hydrogen bondingdonor sites. The guanidinium-based receptors show more selectivity towards the amino alcohol than that of theuryl based ones due to its charge reinforced hydrogen bonds. The conversion efficiency of

The first novel rhodamine B based sensor, rhodamine B hydrazide methyl 5-formyl-1H-pyrrole-2-carboxylate Schiff base (2) capable of detecting both Cu(2+) and Hg(2+) using two different detection modes has been designed and synthesized. The metal ion induced optical changes of 2 were investigated in MeOH:H(2)O (3:1) HEPES buffered solution at pH 7.4. Sensor 2 exhibits selective colorimetric recognition of Cu(2+) and fluorogenic recognition of Hg(2+) with UV-vis and fluorescence spectroscopy, respectively. Moreover, both of the Cu(2+) and Hg(2+) recognition processes are proven to be hardly influenced by other coexisting metal ions.

Bis-pyrene derivative 1, bearing two pyrene and pyridine groups, was synthesized as a ratiometric fluorescent chemosensor for Ag(+) in aqueous solution. Fluorescent chemosensor 1 displayed a selective ratiometric change with Ag(+), which was attributed to the excimer-monomer emissions of pyrenes. A mechanism for the binding mode was proposed based on fluorescence changes, NMR experiments, and theoretical calculations.

Rhodamines are an important cl ass of fluorogenic and chro-mogenic probes, which are the ideal platforms for development of colorimetric chemosensors for specific heavy and transition metal ions. They have excellent spectroscopic properties such as long-wavelength emission, high fluorescence quantum yield, and large molar extinction coefficient. Recently, utilization of rhodamine spirolactam ring-opening process for the detection of metal ions have been well documented.

In most of these studies, molecular recognition is based on non-covalent interac-tions such as hydrogen bonding, metal coordination, and hydro-phobic interactions. In contrast, reversible covalent bond, more specifically imine formation has been rarely explored for the recognition studies. When compared to non-covalent interac-tions, imine bonds

A novel rhodamine-based chemosensor has been designed and synthesized. The chemosensor, a colorless and nonfluorescent compound, exhibited remarkable fluorescent and colorimetric response toward Fe3+ in aqueous media with high selectivity and sensitivity, and no significant response toward other metal ions such as Hg2+, Ag+, Pb2+, Sr2+, Ba2+, Cd2+, Ni2+, Co2+, Fe2+, Mn2+, Cu2+, Zn2+, Ce3+, Mg2+, K+, and Na+.

New receptors 1-3 that bind stereoselectively amino alcohols and convert chirality of amino acidsvia imine bond formation were synthesized. The receptors have uryl (1), thiouryl (2) and guanidinium (3) groups all with additional phenylcarbonyl motifs, which are effective hydrogen bonding donors and play a key role in the stereoselective recognitions. The stereoselectivities were measured from the integration of 1 H NMR peaks. Compound 1 and 2 showed the stereoselectivities for the imine formation with amino alcohols (KR/KS) in the range of 2 ~ 4, and compound 3 in the range of 4 ~ 8. Chirality conversion efficienciesof 1-3 for amino acids, i.e. D/L ratio at equilibrium, are in the range of 1.5 ~ 5.6, showing a little higher efficiency with 3. The additional phenylcarbonyl motifs in 1-3 were revealed not to contribute to significant enhancement of the selectivities.

with an amino acid is associated with the hydrogen bond donating sites (HBD), which plays a decisive role. In order to enhance the stereoselectvity of dipeptides, we speculated that additional HBD’s are required along with the uryl group, for effective hydrogen bonding with both the amide and carboxylate group of the peptides. Hence, we designed compound