Bidentate Chelating Coordination Research Articles

Two new coordination polymers involving Mn(II), Co(II), dicyanamide anion and the nitrogen ligand 5,5′-dimethyl-2,2′-dipyridine: Crystal structures and magnetic properties

Two new compounds [Mn(dca)2(dmdpy)] (1) and [Co(dca)2(dmdpy)] (2) (dca=dicyanamide and dmdpy=5,5′-dimethyl-2,2′-dipyridine) were synthesized and characterized by single crystal X-ray diffraction, FTIR, thermal analysis and magnetic measurements. In both compounds, the dmdpy ligand adopts a bidentate chelating coordination mode while dca anions act as bidentate μ1,5 bridging ligand and the metal centers are involved in a distorted octahedral geometry. In compounds 1 and 2, dca ligands connect the metal sites giving rise to 1D and 2D coordination polymers, respectively. Weak antiferromagnetic interactions were observed between the metal centers in both compounds.

Bis(4-benzoyl-3-methyl-1-phenyl-4,5-dihydro-1H-pyrazol-5-olato-κ2O,O′)(methanol-κO)dioxidouranium(VI) methanol monosolvate

In the title compound, [U(C17H13N2O2)2O2(CH3OH)]·CH3OH, the UVI ion is coordinated by seven O atoms in a distorted pentagonal–bipyramidal geometry with two 3-methyl-1-phenyl-4-benzoyl-4,5-dihydro-1H-pyrazol-5-olate groups with two O atoms in a bidentate chelating coordination mode and by three O atoms, one of which is from a methanol ligand. The crystal packing can be described by alternating layers of complex mol­ecules along the a axis. The structure is stabilized by O—H⋯N and O—H⋯O hydrogen bonding and van der Waals inter­actions.

Abnormal conformation change of an asymmetrical triaryltriazole before and after its coordination

A new asymmetrical substituted triaryltriazole ligand, 3-( p-methoxyphenyl)-4-( p-bromophenyl)-5-(2-pyridyl)-1,2,4-triazole ( L) and its complexes, trans-[MnL 2(NCS) 2] ( 1) and trans-[CuL 2(ClO 4) 2] ( 2), have been successfully synthesized and characterized by UV, IR, ESI-MS, elemental analyses and single-crystal X-ray diffraction methods. In the structure, two L ligands are mainly stabilized by two kinds of intermolecular π⋯ π interactions. In the complexes, each L ligand involves a chelating bidentate coordination mode via N atom of pyridyl group and one N atom of the triazole. Both complexes show a distorted octahedron containing two trans-coordinated anions in 1 with NCS − but in 2 with ClO 4 - . The dihedral angle between the pyridyl and triazole ring in the free L ligand, 1 and 2 is 0.8(2)°, 12.8(2)° and 9.3(2)°, respectively, which represents the first example that the triazole–pyridyl twist angle in the complexes of any triaryltriazole is larger than that in the free L ligand.

Copper(II) complexes based on a new chelating 4-(3,5-diphenyl-1 H-pyrazol-1-yl)-6-(piperidin-1-yl)pyrimidine ligand: Synthesis and crystal structures. Lone pair–π, C–H···π, π–π and C–H···A (A = N, Cl) non-covalent interactions

A new bidentate chelating pyrazolylpyrimidine ligand bearing a strong electron-donating substituent, i.e. 4-(3,5-diphenyl-1 H-pyrazol-1-yl)-6-(piperidin-1-yl)pyrimidine (L) ( Scheme 1), has been synthesized and used to obtain the copper(II) complexes by reaction with CuCl 2. The molar ratio Cu:L = 1:2 leads to isolation of a complex having CuL 2Cl 2 empirical formula, while the molar ratio Cu:L = 1:1 gives a complex with CuLCl 2 empirical formula. The crystal structure of L as well as the structures of both complexes were studied by single crystal X-ray diffraction. The crystal structure of CuL 2Cl 2 compound is formed by trans-[CuL 2Cl 2] mononuclear molecules. Surprisingly, in contrast to the previous compound having molecular structure, the crystal structure of CuLCl 2 consists of mononuclear [CuL 2Cl] + complex cations and dinuclear [Cu 2Cl 6] 2− anions. Thus, formula of CuLCl 2 complex can be represented as [CuL 2Cl] 2[Cu 2Cl 6]. In both complexes molecules of L adopt bidentate chelating coordination mode through N 2 atom of pyrazole and N 3 atom of pyrimidine rings forming five-membered CuN 3C metallocycles. Owing to C–H···N interactions and π–π-stacking L molecules form 2D network. In the structure of trans-[CuL 2Cl 2] there exist double lone pair(N(piperidine))–π(pyrimidine) interactions and C–H···Cl contacts resulting in the formation of 1D chains. Layered 2D structure of [CuL 2Cl] 2[Cu 2Cl 6] results from C–H···Cl, C–H···π and double lone pair(Cl([CuL 2Cl] + complex cation)–π(pyrimidine) interactions.

Effect of a Single-Amino Acid Substitution of the 43 kDa Chlorophyll Protein on the Oxygen-Evolving Reaction of the Cyanobacterium Synechocystis sp. PCC 6803: Analysis of the Glu354Gln Mutation

We constructed a mutant (CP43-Glu354Gln) of the cyanobacterium Synechocystis sp. PCC 6803 in which the glutamic acid at position 354 of the 43 kDa chlorophyll protein (CP43) was replaced with glutamine. To determine the effect of this mutation on the reaction processes of the Mn cluster in the oxygen-evolving complex, we mainly analyzed the spectroscopic properties, including Fourier transform infrared (FTIR) spectroscopy, of photosystem II core complexes. Mutant cells exhibited a lower oxygen-evolving activity than wild-type cells, and an altered pattern of flash-dependent delayed luminescence. This phenotype differed somewhat from an earlier report of the same mutant [Strickler, M. A., et al. (2008) Philos. Trans. R. Soc. London, Ser. B 363, 1179-1187]. FTIR difference spectroscopy revealed that CP43-Glu354 functions as a ligand to the Mn cluster, most likely with bridging bidentate coordination to two Mn ions in the S(1) state and chelating bidentate coordination to a single Mn ion in the S(2) state. A single water molecule was bound to the same Mn atom to which CP43-Glu354 was ligated, and this Mn atom was oxidized in the S(1)-to-S(2) transition. This is the first report on a binding site of a water molecule relevant to a specific amino acid ligand. We found that the Mn ion or ligand that is oxidized in the S(2)-to-S(3) transition was not directly coupled to CP43-Glu354. While the definitive assignment of ligation to the Mn atoms is still under debate, our identification of a novel water binding site will lead to new insights into the oxygen evolution mechanism.

Clarification of the binding model of lead(II) with a highly sensitive and selective fluoroionophore sensor by spectroscopic and structural study

The detection of lead ion is very important both in environment and in biological systems because of its toxicity. A fluoroionophore sensor, N-[4(1-pyrene)-butyroyl]- l-tryptophan (PLT), distinguishing Pb 2+ from other 12 metal ions and exhibiting a very high sensitivity (0.15 μM) in aqueous solution, has been reported. The present study describes the spectroscopic clarification of the intrinsic differences of the binding model between PLT with Pb 2+ and with other ions. The fluorescent property of solid metal carboxylates reflects a character of the metal complex in solution, which results in a facility to solve problems by using solid sample of complex and vibrational spectroscopy. Both FT-infrared and Raman spectroscopy are employed to clarify the binding model between lead ion and its high sensitive and selective fluoroionophore sensor PLT, and essentially to explain why the metal ions other than Pb 2+ cannot response to PLT. The IR spectral data clearly show that a bridging bidentate coordination occurs when PLT is coordinated with Cu 2+ and Zn 2+; while a chelating bidentate coordination between the carboxyl anion and Pb 2+ exists in PLT–Pb, which is a new information beyond the NMR results in previous report. Meanwhile, the present study also indicates a characteristic interaction of lead ion and indole ring as well as the hydrogen bonding between amide groups. Furthermore, the quantum chemical calculations at the DFT level confirm the spectral and structural information of PLT–Pb 2+ proposed by experiments. Thus, the type of coordination, the interaction of the indole ring with the metal ion, and the hydrogen bonding between amide groups in PLT–Pb are likely responsible for the high selectivity of PLT to the lead(II) ion.

Structural and fluorescent characterizations of one- and two-dimensional Cd(II) metal-organic frameworks

Benzimidazole-5-carboxylate (HL1) and 5-methylbenzimidazole-6-carboxylic acid (HL2) have been employed to assemble with Cd(II) ions under hydrothermal conditions, leading to the generation of 1D ( 1) and 2D ( 2) metal-organic frameworks. The two coordinated water molecules of cadmium in 1 restrain the carboxylic moiety from adopting a bidentate chelating coordination mode, which seems to be an important factor in the dramatic structural change from 1D to 2D. Both complexes display blue emission in the solid state and the luminescent properties relate to their structures.

Complexation of Molybdenum(V) with Glycolic Acid: An Unusual Orientation of Glycolato Ligand in {Mo2O4}2+ Complexes

(PyH)5[Mo(V)OCl4(H2O)]3Cl2 and (PyH)n[Mo(V)OBr4]n reacted with glycolic acid (H2glyc) or its half-neutralized ion (Hglyc(-)) to afford a series of novel glycolato complexes based on the {Mo(V)2O4}2+ structural core: (PyH)3[Mo2O4Cl4(Hglyc)]. (1)/ 2CH 3CN (1), (PyH) 3[Mo 2O 4Br 4(Hglyc)].Pr(i)OH(2), (PyH)2[Mo2O4(glyc) 2Py 2] (3), (PyH) 4[Mo 4O 8Cl 4(glyc) 2].2EtOH (4), and [Mo 4O 8(glyc) 2Py 4] (5) (Py = pyridine, C 5H 5N; PyH(+) = pyridinium cation, C 5H 5NH (+) and glyc (2-) = a doubly ionized glycolate, (-)OCH 2COO (-)). The compounds were fully characterized by X-ray crystallography and infrared spectroscopy. The Hglyc (-) ion binds to the {Mo 2O 4} (2+) core through a carboxylate end in a bidentate bridging manner, whereas the glyc (2-) ion adopts a chelating bidentate coordination through a deprotonated hydroxyl group and a monodentate carboxylate. The orientations of glyc (2-) ions in 3- 5 are such that the alkoxyl oxygen atoms occupy the sites opposite the multiply bonded oxides. {(C6H5) 4P}[Mo(VI)O 2(glyc)(Hglyc)] ( 6), an oxidized complex, features a reversed orientation of the glyc(2-) ion. The theoretical DFT calculations on the [Mo(V)2O4(glyc) 2Py 2](2-) and [Mo(VI)O2(glyc)2](2-) ions confirm that binding of glycolate with the alkoxyl oxygen to the site opposite the MoO bond is energetically more favorable in {Mo(V)2O4}(2+) species, whereas a reversed orientation of the ligand is preferred in Mo(VI) complexes. An explanation based on the orbital analysis is put forward.

The first dinuclear orotate complex: Syntheses, spectral, thermal and structural characterization of supramolecular orotate complexes of nickel(II) and copper(II) with 2-hydroxyethylpyridine

Two novel orotate complexes, mononuclear [Ni(HOr)(H 2O) 2(etpy)]·H 2O ( 1) and dinuclear [Cu(μ-HOr)(etpy)] 2 ( 2) (etpy = 2-hydroxyethylpyridine, HOr 2− = dianionic orotate), have been prepared and characterized by elemental analyses, spectroscopic (IR, UV–vis), thermal, magnetic and single crystal X-ray diffraction studies. The mononuclear Ni(II) complex crystallizes in the triclinic space group P 1 ¯ and the dinuclear copper(II) complex crystallizes in the monoclinic space group P2 1/ c. The mononuclear complex consists of individual units in which nickel(II) lies on the inversion center and has octahedral coordination by bidentate HOr 2−, bidentate etpy and two aqua ligands. The dinuclear copper(II) complex composed of a double-orotate bridge and bidentate etpy ligands. Each HOr 2− ligand simultaneously exhibits chelating bidentate and bridging coordination modes. HOr 2− is tricoordinated to one copper atom through N3 atom of pyrimidine ring, one oxygen atom of the carboxylate group as a bidentate ligand and to the other copper ion via the other oxygen of the carboxylate group. The structural units are joined into the framework by the hydrogen bonds in 1 and 2.

Novel Metal Coordinations in the Monolayers of an Amino-Acid-Derived Schiff Base at the Air−Water Interface and Langmuir−Blodgett Films

The metal coordinations in the monolayers of an amino-acid-derived Schiff base, 4-(4-dodecyloxy)-2-hydroxybenzylideneamino)benzoic acid (DSA), at the air−water interface and Langmuir−Blodgett (LB) films have been investigated using surface pressure−area isotherms, infrared reflection absorption spectroscopy (IRRAS), FTIR (transmission and reflection absorption), and UV−vis spectroscopy, respectively. A combination of the three modes of infrared spectroscopy is employed to study interfacial metal coordinations on different substrates (water, CaF2, and gold). The DSA molecules form a condensed monolayer on pure water, in which the Schiff base segments take a nonplanar conformation and their long axes are oriented almost perpendicular to the water surface. The CN stretching bands are assigned for the monolayers on the H2O-based subphases. In the presence of Ca2+ and Zn2+ in the subphases, the monolayers are expanded to a certain extent. Ca2+ and Zn2+ ions only coordinate to the carboxylate oxygen atoms in the fashion of chelating bidentate coordination but not to the imino nitrogen atoms or phenolate oxygen atoms of the salicylideneamino moieties. The long axes of the Schiff base segments are preferentially oriented along the monolayer normals. The twist angle for the nonplanar conformations of the Schiff base segments is considered to increase in the case of Ca2+ and decrease in the case of Zn2+ in comparison with that on pure water. In the presence of Cu2+, the monolayer is expanded and the alkyl chains are disordered. Cu2+ ions coordinate not only to the carboxylate groups in the fashion of bridging bidentate coordination but also to the salicylideneamino moieties. The Schiff base segments are significantly tilted away from the monolayer normal.

First examples of ternary lanthanide 5-aminoisophthalate complexes: Hydrothermal syntheses and structures of lanthanide coordination polymers with 5-aminoisophthalate and oxalate

Two new lanthanide coordination polymers with mixed-carboxylates, [Ln(OX)(HAPA)(H 2O)] n [Ln = Eu ( 1), Ho ( 2); H 2APA = 5-aminoisophthalic acid; OX = oxalate] were obtained by hydrothermal reactions, and characterized by single crystal X-ray diffraction, elemental analysis and IR spectra. Complexes 1 and 2 are both 3-D supramolecular structure, in which lanthanide ions are bridged by oxalate and 5-aminoisophthalate ligands forming 2-D metal–organic framework, and 2-D networks are further architectured to form 3-D supramolecular structures by hydrogen bonds. The two carboxylate groups of H 2APA ligand are all deprotonated and exhibit chelating and bridging bidentate coordination modes, respectively, and the amino group in HAPA presents – NH 3 + in the titled complexes. The thermogravimetric analysis was carried out to examine the thermal stability of the titled complexes. And the photoluminescence property of 1 was investigated.

Preparation, crystal structures and spectroscopic characterization of oxalate copper(II) complexes containing the nitrogen ligands 4,4′-dimethyl-2,2′-bipyridine and di(2-pyridyl)sulfide

The preparation, crystal structures and spectroscopic characterization of four oxalate copper(II) complexes containing the 4,4′-dimethyl-2,2′-bipyridine (Mebpy) or di(2-pyridyl)sulfide (DPS) nitrogen ligands namely [μ-(ox){Cu(Mebpy)(NO 3)(H 2O)} 2] ( 1), [μ-(ox){Cu(Mebpy)(ClO 4)(H 2O)} 2] ( 2), [μ-(ox){Cu(DPS)(H 2O)} 2](ClO 4) 2 ( 3) and [Cu(DPS)(ox)(H 2O)] · 2H 2O ( 4) are described. X-ray diffraction measurements have shown that complexes 1– 3 are binuclear, in which the oxalate anion bridges two Cu(II) centers, while the complex ( 4) is mononuclear and the oxalate anion adopts the terminal bidentate chelating coordination mode. In 1 and 2 the Cu(II) sites display a distorted octahedral geometry (4+2 environment) and in compounds 3 and 4 the Cu(II) centers exhibit a slightly distorted square pyramidal geometry. In addition, complexes 1 and 2 present a 2D supramolecular arrangement through hydrogen bonds between coordination water molecules and nitrate or perchlorate anions and π-stacking interaction between the pyridyl rings of Mebpy nitrogen ligands.

FTIR Spectroscopic Study on the Interaction between a Fluoroionophore and Metal Ions

A fluoroionophore sensor, N-[4-(1-pyrene)butyroyl]-L-tryptophan (PLT), has been reported. It can distinguish lead ion from other 12 metal ions via forming a pyrene dimer and it exhibits a very high sensitivity (0.15 microM) in aqueous solution (Chem. Commun., 2006, 2702). When the indole moiety in PLT was changed to benzene, in forming a new fluoroionophore of N-[4-(1-pyrene)butyroyl]-L-phenylalanine (PLP), it could not form a pyrene dimer in response to Pb(2+) in water. The present study describes the spectroscopic clarification of the intrinsic differences of the binding model between PLP and PLT in binding with Pb(2+). The model shows identical chelating bidentate coordination between COO(-) and Pb(2+) both in PLP-Pb and PLT-Pb; however, there is no indication of the interaction between the phenyl ring and the metal ion or the hydrogen bonding between amide groups in PLP-Pb. These differences in the binding model between PLP-Pb and PLT-Pb illustrate that the indole ring in PLT appears to play a crucial role in the high selectivity and sensitivity of PLT to lead(II) ion.

Magnetic, thermal and spectral properties of Ni(II) 2,3- , 3,5- and 2,6-dimethoxybenzoates

Complexes of Ni(II) 2,3-, 3,5- and 2,6-dimethoxybenzoates have been synthesized, theirphysico-chemical properties have been compared and the influence of the position of –OCH3 sub-stituent on their properties investigated. The analysed compounds are crystalline, hydrated salts withgreen colour. The carboxylate ions show a bidentate chelating or bridging coordination modes. Thethermal stabilities of Ni(II) dimethoxybenzoates were investigated in air in the range of 293-1173 K.The complexes decompose in three steps, yelding the NiO as the final product of decomposition. Theirsolubilities in water at 293 K are in the order of 10 -2 -10 -4 mol⋅dm -3 . The magnetic susceptibilities forthe analysed dimethoxybenzoates of Ni(II) were measured over the range of 76-303 K and the mag-netic moments were calculated. The results reveal that the complexes are the high-spin ones and theligands form the weak electrostatic field in the octahedral coordination sphere of the central Ni(II) ion.The various position –OCH3 groups in benzene ring cause the different steric, mesomeric and induc-tive effects on the electron density in benzene ring.

Syntheses, structures and magnetic properties of Co(II) complexes based on H 4BTEC and 2-( n-pyridyl)benzimidazole ( n = 2, 3, and 4)

The hydrothermal reactions of cobalt(II) salts with 1,2,4,5-benzenetetracarboxylic acid (H 4BTEC) and 2-( n-pyridyl)benzimidazole ( n = 2, 3, 4) led to the formation of three new coordination complexes, Namely, [Co(BTEC) 0.5(2-PyBIm) · H 2O] · H 2O ( 1), [Co(BTEC) 0.5(3-PyBIm) · H 2O] ( 2), [Co(H 2BTEC)(4-PyBIm) 2] · H 2O ( 3) were studied. The H 4BTEC ligands adopt different coordination modes according to the orientation of the pyridyl-sustituted benzimidazole. In complex 1, the BTEC 4− acts as four-dentate bridging ligand with all carboxylate groups adopt unidentate coordination fashion, leading a two-dimensional coordination network. While in 2, two of the four carboxylate groups adopt chelating bi-dentate coordination mode, and the others demonstrate uni-dentate coordination fashion; leading a one-dimensional chain with the nearest Co ⋯ Co separation being 5.057 Å. In 3, the adjacent carboxylate groups chelate the cobalt(II) atom in the uni-dentate coordination fashion, leading a one-dimensional undulating chain. Finally, all the complexes are extended into three-dimensional framework via hydrogen-bonding as well as π–π interactions. The thermal stabilities and temperature-dependent magnetic susceptibilities for the three complexes were also studied.

Magnetic, thermal and spectral properties of Ni(II) 2,3- , 3,5- and 2,6-dimethoxybenzoates

Complexes of Ni(II) 2,3-, 3,5- and 2,6-dimethoxybenzoates have been synthesized, their physico-chemical properties have been compared and the influence of the position of -OCH3 substituent on their properties investigated. The analysed compounds are crystalline, hydrated salts with green colour. The carboxylate ions show a bidentate chelating or bridging coordination modes. The thermal stabilities of Ni(II) dimethoxybenzoates were investigated in air in the range of 293-1173 K. The complexes decompose in three steps, yelding the NiO as the final product of decomposition. Their solubilities in water at 293 K are in the order of 10-2-10-4 mol×dm-3. The magnetic susceptibilities for the analysed dimethoxybenzoates of Ni(II) were measured over the range of 76-303 K and the magnetic moments were calculated. The results reveal that the complexes are the high-spin ones and the ligands form the weak electrostatic field in the octahedral coordination sphere of the central Ni(II) ion. The various position -OCH3 groups in benzene ring cause the different steric, mesomeric and inductive effects on the electron density in benzene ring.

Synthesis and Crystal Structures of Two Metal Complexes Incorporating Malonate and Organodiamine Ligands

Investigation on novel organic-inorganic hybrid framework assemblies represents one of the most active areas of material science and chemical research. Major advances have been made in these materials due to their interesting properties and potential in various applications, e.g., electrical conductivity, magnetism, host-guest chemistry, ion exchange, catalysis, nonlinear optics, etc. Moreover, discovery and design of such new materials with specific networks remain of a particularly important and active subject in the field of supramolecuar chemistry and crystal engineering. A variety of complexes with interesting compositions and topologies have been prepared through taking certain factors into account, such as the coordination nature of the metal ion and the shape, functionality, flexibility, and symmetry of organic ligand. Recently, some dicarboxylate ligands, such as oxalate, malonate, and terephthalate, have been widely used in the construction of these interesting structures. Among them, the malonate dianion can function as a versatile bridging ligand, and the complexity of its structure is associated with the simultaneous adoption of chelating bidentate and different carboxylate bridging coordination modes like syn-syn, syn-anti and anti-anti. On the other hand, an example of the advance in the field of supramolecular chemistry and crystal engineering is the generation of polymeric structures by applying carboxylate bridging ligands together with organodiamine ligands (such as 4,4'-, 2,2'-bypyridine and 1,10-phenanthroline). A larger number of this type of complexes have been synthesized and characterized recently, whereas the structural chemistry of metal complexes incorporating mixed malonate and organodiamine ligands has been less studied. In the present work we report the synthesis and X-ray crystal structures of two new malonato complexes incorporating organodiamine ligands: [Ni(phen)(mal)(H2O)2]·3H2O (H2mal = malonic acid, phen = 1,10-phenanthroline) (1) and [Zn(bpy)(H2O)]2[Zn(bpy)(mal)(H2O)2]2(NO3)4·4H2O (bpy = 2,2'-bipyridine) (2).

Synthesis, Structure, and Luminescent Properties of Guanidinate‐Based Terbium Complexes

AbstractTwo guanidinate‐based terbium complexes [iPrNC(NiPr2)NiPr]mTbCl3–m [m = 3 (1), 2 (2)] were synthesized, and the crystal structure of 1 was determined by single‐crystal X‐ray diffraction. Complexes 1 and 2 were further characterized by elemental analysis, IR, and 1H NMR spectroscopy. In complex 1 the guanidinate ligand coordinates to the terbium atom through the nitrogen atoms in a bidentate chelating coordination mode. As a result of an efficient energy transfer from the guanidinate ligand to the central Tb3+, both 1 and 2 have been found to exhibit strong green emission corresponding to Tb3+ 5D4‐7FJ (J = 6, 5, 4, 3) transitions. Among them, the emission 5D4‐7F5 (550 nm) is the most prominent. The lifetimes of the 5D4 Tb3+ excited levels of the two complexes were determined to be around 0.90 ms. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)

Copper(II)–malonato coordination frameworks with ethanolammonium cations. Synthesis, spectral, thermal and structural characterization of trans-[Cu(mal) 2(meaH) 2] and {(deaH) 2[Cu(μ-mal) 2]·H 2O} ∞ (meaH=monoethanolammonium, deaH=diethanolammonium and mal=malonate)

Two isomorphous malonato–copper(II) complexes, [Cu(mal) 2(meaH) 2] and {(deaH) 2[Cu(μ-mal) 2]·H 2O} ∞ (meaH=monoethanolammonium, deaH=diethanolammonium and mal=malonate), have been prepared and characterized by elemental analyses, IR, UV–vis, magnetic measurements and single crystal X-ray diffraction. The mononuclear complex crystallizes in the monoclinic space group P2 1/ n, with a=8.6630(8) Å, b=7.5122(5) Å, c=11.4390(10) Å, β=95.530(7) and Z=2. The polymeric malonato-bridged copper(II) complex crystallizes in the monoclinic space group P2 1/ c, with a=26.5169(14) Å, b=8.2544(5) Å, c=9.5243(5) Å, β=96.256(4) and Z=4. The monomeric complex consists of individual units in which copper(II) sits on the inversion center and is octahedrally coordinated by two bidentate mal and two monodendate meaH ligands. The structural units are joined into the framework by the system of hydrogen bonds. The polymeric complex composed of two-dimensional chains containing the mal bridged [Cu(mal) 2] 2− ions and each mal ligand simultaneously exhibits chelating bidentate (at one copper atom) and bridging (at the adjacent copper atom) coordination modes. The intrachain Cu1⋯Cu2 separation is 6.302(4) Å. The deaH cations are not coordinated to copper(II) and occupy the voids of the frame work, together with the lattice water molecules. The IR spectra and thermal decompositions of both complexes are described in detail.

Detection of NH Stretching Signals from the Monolayers of Amino Acid Amphiphiles at the Air−Water Interface and Change of Hydrogen Bond Depending on Metal Ion in the Subphase: Infrared Reflection−Adsorption Spectroscopy

The monolayers of amino acid amphiphiles at the air−water interface on pure water and ion-containing subphases have been studied using infrared reflection−absorption spectroscopy. It is the first time that the NH stretching signals are detected from the monolayers at the air−water interface with this technique. In the presence of Ag+ and Pb2+ in the subphases, the covalent interaction between metals and carboxylate groups is predominant in the form of chelating and/or bridging bidentate coordination, and the intermolecular hydrogen-bonding interaction between the adjacent molecules through amide groups is increased in comparison with that in the case of pure water. In the presence of Ca2+ and Cu2+, the ionic interaction between metal ions and carboxylate groups is preferred, and the intramolecular hydrogen bond is developed. The hydrogen bond in the monolayers at the air−water interface undergoes an obvious change in type and strength depending on metal ion in the subphase.