Abstract:Abstract. [Cd(C3H6NOz)2].3H20 , M r --342.6, trigonal, P3121, a = 6.376 (3), c = 25.59 (2)/~, V= 901 (1) ,&3, Z=3, Dx=l.86(4)gcm -3, MoKa, 2=0.7107,/t, /1 = 18.4 cm -1, F(000) = 516, T= 298 K, R = 0.031, wR = 0.040 (w = 1) for 1109 independent reflexions. The metal coordination is octahedral; two alanine molecules are coordinated to the Cd atom as a bidentate ligand with a cis-O,O-trans-N,N donor set while the other two coordination positions are occupied by oxygen atoms of water molecules. The amino groups, c… Show more
“…The Cd−O bond distances are in the range from 2.225(3) to 2.354(3) Å, very similar to corresponding distances in other cadmium octahedral complexes including {Cd 2 (C 4 H 4 O 6 ) 2 (H 2 O)]·3H 2 O} n (2.188(3)−2.425(3) Å), the octahedral sites in Cd 2 (C 3 H 2 O 4 ) 2 (H 2 O) 4 (2.225(4)−2.296(4) Å), [Cd(C 3 H 6 NO 2 ) 2 ]·3H 2 O (2.296(4)−2.326(5) Å), Cd(C 4 H 2 O 4 )·2H 2 O (2.224(5)−2.521(5) Å), and the octahedral site in cadmium maleate (2.226(5)−2.317(5) Å) . Overall, the citrate ligand plays the role of a tridentate metal chelator, participating in the octahedral environment around Cd(II) and joining abutting Cd(II) ions in the lattice.…”
The presence of cadmium in the environment undoubtedly contributes to an increased risk of exposure and ultimate toxic influence on humans. In an effort to comprehend the chemical and biological interactions of Cd(II) with physiological ligands, like citric acid, we explored the requisite aqueous chemistry, which afforded the first aqueous Cd(II)-citrate complex [Cd(C(6)H(6)O(7))(H(2)O)](n)() (1). Compound 1 was characterized by elemental analysis, and spectroscopically by FT-IR and (113)Cd MAS NMR. Compound 1 crystallizes in the orthorhombic space group P2(1)2(1)2(1), with a = 6.166(2) A, b = 10.508(3) A, c = 13.599(5) A, V = 881.2(5) A(3), and Z = 4. The X-ray structure of 1 reveals the presence of octahedral Cd(II) ions bound to citrate ligands in a molecular crystal lattice. Citrate acts as a tridentate binder promoting coordination to one Cd(II) through the central alcoholic moiety, one terminal carboxylate group, and the central carboxylate group. In addition, the central carboxylate binds to three Cd(II) ions. Specifically, one of the oxygens of the central carboxylate serves as a bridge to two neighboring Cd(II) ions, while the other oxygen binds to a third Cd(II). A bound water molecule completes the coordination requirements of Cd(II). (113)Cd MAS NMR studies project the spectroscopic signature of the nature of the coordination environment around Cd(II) in 1, thus corroborating the X-ray findings. Collectively, the data at hand are in line with past solution studies. The latter predict that other similar low molecular mass Cd(II)-citrate complexes may exist in the acidic pH region, thus influencing the uptake of cadmium by living (micro)organisms, their ability to metabolize organic substrates, and possibly Cd(II) toxicity.
“…The Cd−O bond distances are in the range from 2.225(3) to 2.354(3) Å, very similar to corresponding distances in other cadmium octahedral complexes including {Cd 2 (C 4 H 4 O 6 ) 2 (H 2 O)]·3H 2 O} n (2.188(3)−2.425(3) Å), the octahedral sites in Cd 2 (C 3 H 2 O 4 ) 2 (H 2 O) 4 (2.225(4)−2.296(4) Å), [Cd(C 3 H 6 NO 2 ) 2 ]·3H 2 O (2.296(4)−2.326(5) Å), Cd(C 4 H 2 O 4 )·2H 2 O (2.224(5)−2.521(5) Å), and the octahedral site in cadmium maleate (2.226(5)−2.317(5) Å) . Overall, the citrate ligand plays the role of a tridentate metal chelator, participating in the octahedral environment around Cd(II) and joining abutting Cd(II) ions in the lattice.…”
The presence of cadmium in the environment undoubtedly contributes to an increased risk of exposure and ultimate toxic influence on humans. In an effort to comprehend the chemical and biological interactions of Cd(II) with physiological ligands, like citric acid, we explored the requisite aqueous chemistry, which afforded the first aqueous Cd(II)-citrate complex [Cd(C(6)H(6)O(7))(H(2)O)](n)() (1). Compound 1 was characterized by elemental analysis, and spectroscopically by FT-IR and (113)Cd MAS NMR. Compound 1 crystallizes in the orthorhombic space group P2(1)2(1)2(1), with a = 6.166(2) A, b = 10.508(3) A, c = 13.599(5) A, V = 881.2(5) A(3), and Z = 4. The X-ray structure of 1 reveals the presence of octahedral Cd(II) ions bound to citrate ligands in a molecular crystal lattice. Citrate acts as a tridentate binder promoting coordination to one Cd(II) through the central alcoholic moiety, one terminal carboxylate group, and the central carboxylate group. In addition, the central carboxylate binds to three Cd(II) ions. Specifically, one of the oxygens of the central carboxylate serves as a bridge to two neighboring Cd(II) ions, while the other oxygen binds to a third Cd(II). A bound water molecule completes the coordination requirements of Cd(II). (113)Cd MAS NMR studies project the spectroscopic signature of the nature of the coordination environment around Cd(II) in 1, thus corroborating the X-ray findings. Collectively, the data at hand are in line with past solution studies. The latter predict that other similar low molecular mass Cd(II)-citrate complexes may exist in the acidic pH region, thus influencing the uptake of cadmium by living (micro)organisms, their ability to metabolize organic substrates, and possibly Cd(II) toxicity.
“…The presence of two sites agrees with a doubling of all 13 C resonances observed for this complex by 13 C MAS NMR (not shown) considering observations made for the analogous Cd-alaninate, Cd-glycinate, and Zn-glycinate complexes. For these complexes the number of distinct 13 C carbonyl resonances matches the number of metal sites identified by XRD. − 7 Experimental (a) and simulated (b−d) 67 Zn QCPMG spectra of Zn(Ala) 2 ·H 2 O. The experimental spectrum was obtained using τ 1 = τ 3 = 68.0 μs, τ 2 = τ 4 = 69.7 μs, τ a = 100 μs, τ d = 122 μs, ω rf /2π = 49.8 kHz, M = 19, a dwell time of 0.2 μs, and 589824 scans.…”
Section: Resultsmentioning
confidence: 96%
“…For these complexes the number of distinct 13 C carbonyl resonances matches the number of metal sites identified by XRD. [28][29][30][31] To the best of our knowledge 87 Sr solid-state NMR has so far been employed only in a single study which specifically addressed the phase transition for strontium titanate (SrTiO 3 ) around 110 K. 54 In analogy to the examples discussed above, this is most likely ascribed to experimental difficulties that may be alleviated using the QCPMG method. This is illustrated by the experimental 87 Sr QCPMG NMR spectra of Sr(NO 3 ) 2 and SrMoO 4 shown in Figures 8a and 9a, respectively.…”
Taking advantage of an order of magnitude in sensitivity enhancement obtained by sampling of quadrupolar-echo (QE) solid-state NMR spectra during a quadrupolar Carr-Purcell-Meiboom-Gill (QCPMG) pulse sequence, we demonstrate that the coordination environment of low-γ quadrupolar metal nuclei can be studied routinely for powders with these nuclei in natural abundance. The general applicability of the method is demonstrated by 39 K, 25 Mg, 67 Zn, and 87 Sr QCPMG solid-state NMR experiments for K 2 MoO 4 , KVO 3 , Mg(VO 3 ) 2 , Zn(CH 3 COO) 2 ‚2H 2 O, Zn(Ala) 2 ‚H 2 O, Sr(NO 3 ) 2 , and SrMoO 4 . For all samples the quadrupolar coupling parameters and the isotropic chemical shifts are extracted by numerical simulation and iterative fitting of the spin-echo sideband spectra observed in the experimental QCPMG NMR spectra. These parameters are discussed in light of the crystal structures for the compounds.
“…A symmetry check by PLATON (Spek 2009) showed that actually the orthorhombic symmetry is correct for both the zinc and cobalt salts. The same arrangement is found in the structure of bis(L-alaninato)-diaqua-cadmium monohydrate (Demaret and Abraham 1987b) Additionally, salts of alkali metals with serine and threonine were reported, but due to the lack of suitable crystals, no XRD experiments were conducted. Instead, (Fig.…”
This chapter deals with salts formed from metal cations and amino acid anions. All amino acids can act as monovalent anion; the acidic members glutamic acid and aspartic acid as well as cysteine and tyrosine can form both monovalent and divalent anions. Due to the large number of available cations, a multitude of combinations is possible and in fact found (for the standard twenty amino acids, over 150 crystal structures are published, and many more species have been characterized by other methods). Different hydration states (as reported for the pristine amino acid crystals) occur as well, and the existence of polymorphs is also documented for some cases. The formation of metal-amino acid complexes has been studied in several works (both for a given amino acid and a given cation), and the flexibility of amino acid molecules as ligands allows coordination of cations with different chemical properties (such as charge or ionic radius). Several coordination modes are found for amino acids -the molecules can act as monodentate, bidentate, tridentate, and bridging ligands. The connectivity of the coordination polyhedra of the metal cations is considered -isolated units are frequent, but chains and layers occur as well. Moreover, these units can connect via amino acid molecules to form higher-dimensional structures. Hydrogen bonds (also involving water molecules, both in coordination or in the interstices as crystal water) further stabilize the units, forming relatively stable phases. The frequency of salts varies among the different amino acids, and most examples are reported for glycinate salts, whereas crystals of cations and basic and weakly soluble amino acids are difficult to obtain (e.g., arginate and lysinate salts have not been reported in crystalline state). Finally, the aspect of symmetry is considered (the chirality of most amino acids playing a crucial role), and, consequently, the properties of these salts have impact on applications in the fields of physics, biology, and medicine.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
