SEVERAL COORDINATION MODES OF 5-AMINO-1,3,4-THIADIAZOLE-2-SULFONAMIDE (HATS) WITH Cu(II), Ni(II) AND Zn(II): MIMETIC TERNARY COMPLEXES OF CARBONIC ANHYDRASE-INHIBITOR

Abstract

The coordination properties of 5-amino-1,3,4-thiadiazole-2-sulfonamide (Hats) with Cu(II), Ni(II) and Zn(II) ions, are analyzed. Although the ligand presents several donor atoms, we have only observed three coordination behaviors: (i) as a monodentate ligand through the N_sulfonamido atom, (ii) as a bridging ligand linking the metal ions through the N_sulfonamido and N_thiadizole atoms and (iii) as a bridging ligand linking metal ions through the N and O atoms of the sulfonamidate group. It is noteworthy that coordination mode (iii) is observed for the first time in heterocyclic sulfonamides complexes. In addition, the conformation of the Hats as counter-ion is analyzed and compared with the conformations that the ligand adopts in metal complexes.     

Theoretical study on the interaction of sulfur‐ and aminopyridine‐containing chelating resins with Hg(II) and Pb(II)

The geometries and energetics of complexes of Hg(II) and Pb(II) with sulfur‐ and aminopyridine‐containing chelating resin including crosslinked polystyrene immobilizing 2‐aminopyridine via sulfur‐containing (PVBS‐AP), sulfoxide‐containing (PVBSO‐AP), and sulfone‐containing (PVBSO₂‐AP) spacer arms have been investigated theoretically, and thus interactions of the metal ions with chelating resins were evaluated. The results indicate that PVBS‐AP behaves as a tridentate ligand to coordinate with the metal ions by S and two N atoms to form chelating compounds with S atom playing a dominant role in the coordination, whereas PVBSO‐AP and PVBSO₂‐AP interact with metal cations, respectively, in a tricoordinate manner by O and two N atoms forming chelating complexes. Furthermore, it is revealed that O and N2 atoms of PVBSO‐AP are the main contributor of coordination to Hg(II), whereas N2 atom of PVBSO₂‐AP is mainly responsible for the coordination to Hg(II). For PVBSO‐AP‐Pb²⁺ and PVBSO₂‐AP‐Pb²⁺ complex, the coordination is dominated by the synergetic effect of N1, N2, and O atoms. Natural bond orbital and second‐order perturbation analyses suggest that the charge transfer from the chelating resins to metal ions is mainly dominated by the interactions of lone pair of electrons of the donor atoms with the unoccupied orbitals of metal ions. Hg(II) complexes exhibit larger binding energies than the corresponding Pb(II) complexes, implying the chelating resins exhibit higher affinity toward Hg(II), which is consistent with the experimental results. Combined the theoretical and experimental results, further understanding of the structural information of the complexes and the coordination mechanism was achieved. © 2010 Wiley Periodicals, Inc. Int J Quantum Chem, 2011     

Theoretical investigation on sulfur‐containing chelating resin‐divalent metal complexes

The complex structures and interactions of sulfur‐containing chelating resin poly[4‐vinylbenzyl‐(2‐hydroxyethyl)]sulfide (PVBS), poly[4‐vinylbenzyl‐(2‐hydroxyethyl)]sulfoxide (PVBSO), and poly[4‐vinylbenzyl‐(2‐hydroxyethyl)]sulfone (PVBSO₂) with divalent metal chlorides (Cu(II), Ni(II), Zn(II), Cd(II), and Pd(II)) were investigated theoretically. Results indicate that PVBS tends to coordinate with metal ions by sulfur and oxygen atoms forming five‐membered ring chelating complexes; while PVBSO and PVBSO₂ prefer to interact with metal ions by the oxygen atom of the sulfoxide or sulfone and hydroxyl group to form six‐membered ring chelating compounds. Theoretical calculations reveal that sulfur atoms of PVBS are the main contributor when coordinate with metal ions, while oxygen atoms also take part in the coordination with Cu(II), Zn(II), and Cd(II). As for PVBSO, the oxygen atoms of sulfoxide group play a key role in the coordination, but sulfur and hydroxyl oxygen also participate in the coordination. Similarly, sulfone group oxygen atoms of PVBSO₂ dominate the coordination of Ni(II), Cu(II), and Pd(II), while the affinities of Zn(II) and Cd(II) are mainly attributed to the hydroxyl oxygen atoms. The computational results are in good agreement with the XPS analysis. Combined the theoretical and experimental results, further understanding of the structural information on the complexes was achieved and the adsorption mechanism was confirmed. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2010     

Synthesis and characterization of Ni(II), Pd(II) and Pt(II) complexes of 2,4-diamino-5-(3, 4, 5-trimethoxybenzyl)pyrimidine complexes

The Ni(II), Pd(II) and Pt(II) complexes of 2,4-diamino-5-(3,4,5-trimethoxybenzyl)pyrimidine (trimethoprim) have been synthesized and characterized by elemental analysis, electronic and IR spectroscopy, and magnetic susceptibility measurements. The single-crystal X-ray structure of the Ni(II) complex is reported. Ni(II) is coordinated to the N(1) atoms of two trimethoprim molecules that act as monodentates. Octahedral coordination around the nickel atom is completed by coordination to two molecules of methanol and two acetate ions. Pd(II) and Pt(II) complexes are square planar and the metal ions coordinate one molecule of trimethoprim, two chloride ions and a molecule of water.     

Thermodynamic, kinetic and solid-state study of divalent metal complexes of 1,4,8,11-tetraazacyclotetradecane (cyclam) bearing two trans (1,8-)methylphosphonic acid pendant arms

Divalent metal complexes of macrocyclic ligand 1,4,8,11-tetraazacyclotetradecane-1,8-bis(methylphosphonic acid)) (1,8-H4te2p, H4L) were investigated in solution and in the solid state. The majority of transition-metal ions form thermodynamically very stable complexes as a consequence of high affinity for the nitrogen atoms of the ring. On the other hand, complexes with Mn2+, Pb2+ and alkaline earth ions interacting mainly with phosphonate oxygen atoms are much weaker than those of transition-metal ions and are formed only at higher pH. The same tendency is seen in the solid state. Zinc(II) ion in the octahedral trans-O,O-[Zn(H2L)] complex is fully encapsulated within the macrocycle (N4O2 coordination mode with protonated phosphonate oxygen atoms). The polymeric {[Pb(H2L)(H2O)2].6H2O}n complex has double-protonated secondary amino groups and the central atom is bound only to the phosphonate oxygen atoms. The phosphonate moieties bridge lead atoms creating a 3D-polymeric network. The [{(H2O)5Mn}2(micro-H2L)](H2L).21H2O complex contains two pentaaquamanganese(II) moieties bridged by a ligand molecule protonated on two nitrogen atoms. In the complex cation, oxygen atoms of the phosphonate groups on the opposite sites of the ring occupy one coordination site of each metal ion. The second ligand molecule is diprotonated and balances the positive charge of the complex cation. Complexation of zinc(II) and cadmium(II) by the ligand shows large differences in reactivity of differently protonated ligand species similarly to other cyclam-like complexes. Acid-assisted dissociations of metal(II) complexes occur predominantly through triprotonated species [M(H3L)]+ and take place at pH < 5 (Zn2+) and pH < 6 (Cd2+).     

Phosphoryl Complexes of Some Metal(II) Trifluoromethanesulfonates

Cobalt(II), nickel(II), copper(II), and zinc(II) trifluoromethanesulfonates form complexes with the phosphoryl ligands hexamethylphosphoric triamide, nonamethyl imidodiphosphoric tetramide, trimorpholinophosphine oxide, tributylphosphine oxide, and triphenylphosphine oxide. The compounds have been prepared by a substitution reaction using trialkyl orthoformates as dehydrating agents and were investigated with the aid of infrared and ligand-field spectroscopy. In all compounds the ligands coordinate via the phosphoryl oxygen atoms. In some complexes the trifluoromethanesulfonate anions are (semi-)coordinated to the metal ions. The coordination around the metal ions was found to be tetrahedral, square pyramidal, or octahedral depending on the particular combination of metal ion and ligand. In its coordination behaviour the CF₃SO₃^? ion resembles the perrhenate ion.     

Interactions of the ethanolamino groups of nanofilms with Co(II), Ni(II), Cu(II), Zn(II), and Cr(III) ammoniates at the surface of PVC plates

Interactions of nanofilms containing ethanolamino groups with cobalt(II), nickel(II), copper(II), and zinc(II) ammoniates at the surface of polyvinylchloride plates and with chromium(III) ammoniate in a solution of ammonium chloride were studied. It was found that the groups of the film, together with chloride ions, displace all ammonia molecules from the inner coordination sphere of the metal. The average number of the ethanolamino N atoms of the film participating in formation of the metal ion coordination sphere is 3.35, 3.47, 3.67, 3.42, and 3.37 for Co²⁺, Ni²⁺, Cu²⁺, Zn²⁺, and Cr³⁺ complexes, respectively. The average number of chloride ions is 2 for Co²⁺, Ni²⁺, Cu²⁺, and Zn²⁺ and 3 for Cr³⁺. The coordination number of the central atoms is 6. The Cr³⁺ ion forms a coordination sphere composed of three N atoms and three chloride ions and a coordination sphere (charged 1+) made up of four N atoms and two chloride ions, with the third chloride ion being in the outer sphere. The Co²⁺, Ni²⁺, and Cu²⁺ ions form uncharged coordination spheres of two types: (1) with four N atoms and two chloride ions and (2) with three N atoms, two chloride ions, and the O atom of the ethanol hydroxyl group.     

Spectral,Thermal, and Antimicrobial Studies on the Copper(II), Zinc(II), Cadmium(II), and Mercury(II) Chelates of a New Antimetabolite–5-Dimethylaminomethyl-2-Thiouracil

Owing to the presence of multiple donor atoms such as N(1)H, C(2)SH, N(3), C(4)O, and CNC in the newly synthesized antimetabolite, namely, 5-dimethylaminomethyl-2-thiouracil, preferences of the hetero-atoms for coordination with metal ions like Cu(II), Zn(II), Cd(II), and Hg(II) were explored. The complexes isolated were characterized by chemical analysis and spectroscopic techniques. The ligand behaves as a bidentate/tetradentate chelating ligand. Invariably in all the complexes, one of the donor atoms is the soft C(2)SH. The kinetic and thermodynamic parameters for the thermal decomposition of the metal chelates were evaluated using (Coats–Redfern) and (Madhusudanan–Krishnan–Ninan) equations. The antimicrobial studies show that the copper(II) complexes are more active than the other complexes.     

The protective effect of salicylic acid on lysozyme against riboflavin-mediated photooxidation

Tridentate Schiff base (H(2)L) ligand was synthesized via condensation of o-hydroxybenzaldehyde and 2-aminothiophenol. The metal complexes were prepared from reaction of the ligand with corresponding metal salts presence of substituted pyridine in two different solvents (MeOH or MeCN). The ligand and metal complexes were then characterized by using FTIR, TGA, (1)H NMR and (13)C NMR spectroscopies. The FTIR spectra showed that H(2)L was coordinated to the metal ions in tridentate manner with ONS donor sites of the azomethine N, deprotonated phenolic-OH and phenolic-SH. Furthermore, substituted pyridine was coordinated to the central metal atoms. The thermal behavior of the complexes was investigated by using TGA method and dissociations indicated that substituted pyridine and ligand were leaved from coordination. This coordination of the metal complexes was correlated by (1)H NMR and (13)C NMR. Finally, electrochemical behavior of the ligand and a Ni(II) complex were investigated.     

Thermal properties of complexes of amaranthus starch with selected metal salts

Metal cations (Cu(II), Fe(III), Mn(II), and Ni(II)) are ligated by amaranthus starch as proven by EPR spectra and conductivity measurements. The hydroxyl groups of starch are the coordination sites. The acetate and nitrate anions of the metal salts behave as bidentate ligands and reside in the inner coordination sphere of resulting polycenter Werner complexes. There is only a weak degeneration of orbitals of central metal ions caused by a shift of unpaired spin from the central atom to the ligand. The ligation of the central metal atoms resulted in a variation of the thermal stability, pathway, and rate of thermal decomposition of starch as proven by thermogravimetric (TG) and differential scanning calorimetric (DSC) measurements.     

Blue dimetallic complexes of two heavy metal ions Cd(II) and Hg(II) with an extended nitrogen donor ligand. Preparation, spectral characterization, and crystallographic studies

In methanol, the metal salts CdCl2.H2O and HgCl2 react instantaneously with the deprotonated ligand, L-, producing molecular dimetallic ink-blue complexes of general formula M2Cl2L2, M=Cd(II), (1) and Hg(II), (2) (HL=2-[2-(pyridylamino)phenylazo]pyridine). Crystal structures of these two complexes are reported. The coordination sphere around each Cd(II) ion in 1 is a distorted square pyramidal. The metal ion (Cd1) sits above the basal plane of three nitrogen atoms, N(1), N(3), and N(4). The second cadmium ion (Cd2) in this compound lies below the plane of three nitrogen atoms, N(6), N(8), and N(9). The apical positions are occupied by two Cl atoms. Secondary intramolecular interactions between the metal ions and the anionic secondary amine nitrogen atoms (N(4) and N(9)) are noted. The geometry of each Hg(II) ion in the mercury complex, Hg2Cl2L2.0.5H2O, is also distorted square based pyramid with the metal ions lying out of planes of the three nitrogen atoms of the chelating ligands. Secondary Hg(1)...N(1A) (deprotonated amine) interactions are noted. The separation between the two Hg(II) ions in this complex is within the sum of their van der Waals radii. Solution properties of these blue complexes are reported. The origin of the intense blue color in these complexes is the intraligand transitions that occur near 615 nm. 1H NMR of Hg2Cl2L2.0.5H2O indicates that it undergoes exchange in solution with the coordinated ligands.     

Dioxadiaza- and trioxadiaza-macrocycles containing one dibenzofuran unit selective for cadmium

The binding properties of dioxadiaza- ([17](DBF)N2O2) and trioxadiaza- ([22](DBF)N2O3), macrocyclic ligands containing a rigid dibenzofuran group (DBF), to metal cations and structural studies of their metal complexes have been carried out. The protonation constants of these two ligands and the stability constants of their complexes with Ca2+, Ba2+, and Mn2+, Co2+, Ni2+, Cu2+, Zn2+ and Cd2+, were determined at 298.2 K in methanol-water (1:1, v/v), and at ionic strength 0.10 mol dm-3 in KNO3. The values of the protonation constants of both ligands are similar, indicating that no cavity size effect is observed. Only mononuclear complexes of these ligands with the divalent metal ions studied were found, and their stability constants are lower than expected, especially for the complexes of the macrocycle with smaller cavity size. However, the Cd2+ complex with [17](DBF)N2O2 exhibits the highest value of stability constant for the whole series of metal ions studied, indicating that this ligand reveals a remarkable selectivity for cadmium(II) in the presence of all the metal ions studied, except copper(II), indicating that this ligand reveals a remarkable selectivity for cadmium(II) in the presence of the mentioned metal ions. The crystal structures of H2[17](DBF)N2O3(2+) (diprotonated form of the ligand) and of its cadmium complex were determined by X-ray diffraction. The Cd2+ ion fits exactly inside the macrocyclic cavity exhibiting coordination number eight by coordination to all the donor atoms of the ligand, and additionally to two oxygen atoms from one nitrate anion and one oxygen atom from a water molecule. The nickel(II) and copper(II) complexes with the two ligands were further studied by UV-vis-NIR and the copper(II) complexes also by EPR spectroscopic techniques in solution indicating square-pyramidal structures and suggesting that only one nitrogen and oxygen donors of the ligands are bound to the metal. However an additional weak interaction of the second nitrogen cannot be ruled out.     

Interaction of Poly(benzoyl thiocarbamate)-Modified Hyperbranched Polyester with Co(II) and Cu(II) Nitrates

The interaction of Co(NO3)2 and Cu(NO3)2 with hyperbranched polyester containing 7 terminal benzoyl thiocarbamate groups has been studied by IR-Fourier and electron absorption spectroscopy. А new polynuclear complexes of Co(II) and Cu(II) with poly(benzoyl thiocarbamate)-modified hyperbranched polyester have been synthesized. It has been found that the oxygen and sulfur atoms of the peripheral benzoyl thiocarbamate fragments of the macroligand are involved in coordination with metal ions, the metal to ligand ratio being 7 : 1.     

The role of copper ions in Tb(III) luminescence sensitization in heterometallic complexes with podands

It has been demonstrated that copper-induced terbium(III) luminescence sensitization in heterometallic complexes with hydrazine-containing podands is caused by the ligand ring closure and joint coordination of both metal ions to the carbonyl oxygen atoms as well as, mainly, by the reduction with the hydrazine substituents of Cu(II) to Cu(I), which is able to sensitize terbium luminescence.     

Ni(II), Cu(II), and Zn(II) dinuclear metal complexes with an aza-phenolic ligand: crystal structures,magnetic properties,and solution studies

The basicity behavior and ligational properties of the ligand 2-((bis(aminoethyl)amino)methyl)phenol (L) toward Ni(II), Cu(II), and Zn(II) ions were studied by means of potentiometric measurements in aqueous solution (298.1 +/- 0.1 K, l = 0.15 mol dm-3). The anionic L-H- species can be obtained in strong alkaline solution; this species behaves as tetraprotic base (log K1 = 11.06, log K2 = 9.85, log K3 = 8.46, log K4 = 2.38). L forms mono- and dinuclear complexes in aqueous solution with all the transition metal ions examined; the dinuclear species show a [M2(L-H)2]2+ stoichiometry in which the ligand/metal ratio is 2:2. The studies revealed that two mononuclear [ML-H]+ species self-assemble, giving the dinuclear complexes, which can be easily isolated from the aqueous solution due to their low solubility. This behavior is ascribed to the fact that L does not fulfill the coordination requirement of the ion in the mononuclear species and to the capacity of the phenolic oxygen, as phenolate, to bridge two metal ions. All three dinuclear species were characterized by determining their crystal structures, which showed similar coordination patterns, where all the single metal ions are substantially coordinated by three amine functions and two oxygen atoms of the phenolate moieties. The two metals in the dinuclear complexes are at short distance interacting together as shown by magnetic measurements performed with Ni(II) and Cu(II) complexes, which revealed an antiferromagnetic coupling between the two metal ions. The [Cu2(L-H)2]2+ cation shows a phase transition occurring by the temperature between 100 and 90 K; the characterization of the compounds existing at different temperatures was investigated using X-ray single-crystal diffraction, EPR, and magnetic measurements.     

Transition metal complexes of the schiff base derivatives of the ligand 1,8-dihydroxy-3,6-dimethyl-2-acetylnaphthalene

New Schiff bases derived from 2-acetyl-1,8-dihydroxy-3,6-dimethylnaphthalene(H₂addn) and 1,2-propanediamine(pn), 2,3-butanediamine(pn) and 1,2-cyclohexyldiamine(chn) have been prepared and characterized as (H₄addn-diam). In this work is reported an improved experimental method which yields well characterized mononuclear species of H₄addn-en and H₄addn-pn with Cu(II), Ni(II) and Co(II). The Cu(II) complex has been studied by esr which unambigously shows a N₂O₂ coordination mode for the metal ion. Based on the spectral characteristics of these complexes we conclude that all metal atoms have the same coordination mode. Only one binulear complex, [NiUO₂(addn-en)] is reported in this work. All attempts to synthesize binuclear complexes with first transition series metal ions were unsuccessful.     

Nitrogen centered inverse coordination complexes. A survey of molecular topologies

Abstract

Inverse coordination is an emerging novel chemical concept describing the formation of metal complexes in which the arrangement of acceptor and donor sites is opposite to that occurring in conventional coordination complexes. Inverse coordination complexes are formed around a non-metal species as central atom (ion or small molecule) surrounded by a number of metal atoms (ions) connected or not by internal bridging (intramolecular) linkers. This article illustrates the diversity of species described under this concept with structures in which the coordination center is nitrogen (mono- and poly-nitrogen moieties).     

Nature of metal binding sites in Cu(II) complexes with histidine and related N-coordinating ligands, as studied by EXAFS

Knowledge of the complexes formed by N-coordinating ligands and Cu(II) ions is of relevance in understanding the interactions of this ion with biomolecules. Within this framework, we investigated Cu(II) complexation with mono- and polydentate ligands, such as ammonia, ethylenediamine (en), and phthalocyanine (Pc). The obtained Cu-N coordination distances were 2.02 A for [Cu(NH(3))(4)](2+), 2.01 A for [Cu(en)(2)](2+), and 1.95 A for CuPc. The shorter bond distance found for CuPc is attributed to the macrocyclic effect. In addition to the structure of the first shell, information on higher coordination shells of the chelate ligands could be extracted by EXAFS, thus allowing discrimination among the different coordination modes. This was possible due to the geometry of the complexes, where the absorbing Cu atoms are coplanar with the four N atoms forming the first coordination shell of the complex. For this reason multiple scattering contributions become relevant, thus allowing determination of higher shells. This knowledge has been used to gain information about the structure of the 1:2 complexes formed by Cu(II) ions with the amino acids histidine and glycine, both showing a high affinity for Cu(II) ions. The in-solution structure of these complexes, particularly that with histidine, is not clear yet, probably due to the various possible coordination modes. In this case the square-planar arrangements glycine-histamine and histamine-histamine as well as tetrahedral coordination modes have been considered. The obtained first-shell Cu-N coordination distance for this complex is 1.99 A. The results of the higher shells EXAFS analysis point to the fact that the predominant coordination mode is the so-called histamine-histamine one in which both histidine molecules coordinate Cu(II) cations through N atoms from the amino group and from the imidazole ring.     

Anti-hepatocellular carcinoma,antioxidant, anti-inflammation and antimicrobial investigation of some novel first and second transition metal complexes

New coordination compounds of some selected metal ions from the first and second transition metals series with a Schiff base were synthesized and characterized. The Schiff base is derived from 4-Aminoantipyrine and 3-(hydroxyimino) butan-2-one. The compounds were characterized by different analysis tools like; elemental analysis, mass spectra, Fourier transform infrared (FTIR) as well as electronic spectra, magnetic measurements, molar conductance and thermal analysis technique. All complexes were formed with 1:1 (metal: ligand) stoichiometry except Mn (II) where 1:2 (Mn: ligand) is formed. Schiff base ligand interacted as a tridentate ligand by using the nitrogen atoms of the imine and the oximato groups and the carbonyl oxygen atom as donor groups with all studied metal ions except copper (II) and manganese (II) where the carbonyl oxygen is not shared in the coordination. These complexes show various physicochemical properties. X-ray powder diffraction shows different crystal systems; Cd (II) complex: hexagonal, Cu (II) complex: orthorhombic; and [Ni (II), Mn (II), Rh (III) & Pd (II)] complexes: monoclinic. All compounds showed potent cytotoxicity against the growth of human liver cancer cell lines. The square planar Pd (II) complex was more active than those of octahedral geometries of all other synthesized complexes. Cd (II) complex has the highest microbial growth inhibition than the rest of the prepared complexes. The docking active sites interactions were evaluated using the selected proteins EGFR tyrosine kinase and protein crystal structure of GlcN-O-P synthase. in vitro antioxidant assay revealed potent free radical scavenging activity of the three synthesized Cu (II), Pd (II) and Rh (III) complexes that exceeded the standard ascorbic acid. Pd (II) complex shows the most significant inhibition denaturation percent.     

A new pyridine-based 12-membered macrocycle functionalised with different fluorescent subunits; coordination chemistry towards Cu(II), Zn(II), Cd(II), Hg(II), and Pb(II)

The coordination chemistry of the new pyridine-based, N2S2-donating 12-membered macrocycle 2,8-dithia-5-aza-2,6-pyridinophane (L1) towards Cu(II), Zn(II), Cd(II), Hg(II), and Pb(II) has been investigated both in aqueous solution and in the solid state. The protonation constants for L1 and stability constants with the aforementioned metal ions have been determined potentiometrically and compared with those of ligand L2, which contains a N-aminopropyl side arm. The measured values show that Hg(II) in water has the highest affinity for both ligands followed by Cu(II), Cd(II), Pb(II), and Zn(II). For each metal ion considered, 1:1 complexes with L1 have also been isolated in the solid state, those of Cu(II) and Zn(II) having also been characterised by X-ray crystallography. In both complexes L1 adopts a folded conformation and the coordination environments around the two metal centres are very similar: four positions of a distorted octahedral coordination sphere are occupied by the donor atoms of the macrocyclic ligand, and the two mutually cis-positions unoccupied by L1 accommodate monodentate NO3- ligands. The macrocycle L1 has then been functionalised with different fluorogenic subunits. In particular, the N-dansylamidopropyl (L3), N-(9-anthracenyl)methyl (L4), and N-(8-hydroxy-2-quinolinyl)methyl (L5) pendant arm derivatives of L1 have been synthesised and their optical response to the above mentioned metal ions investigated in MeCN/H2O (4:1 v/v) solutions.