Syntheses, crystal structure and ab initio calculations of two new phosphoric triamides

The reaction of N-benzoylphosphoramidic dichloride with piperidine and 4-methylpiperidine lead to PhC(O)N(H)P(O)R₂ with R=piperidine (1) and R=4-methylpiperidine (2) as N-benzoyl-N′,N″-bis(piperidine) phosphoric triamide and N-benzoyl-N′,N″-bis(4-methylpiperidine) phosphoric triamide, respectively. The products have been characterized by ¹H, ¹³C, ³¹P NMR spectra, and by elemental analysis. The crystalline solid for (1) and (2) consists surprisingly of four and two independent molecules, respectively. There is a disorder in one amine group due to ring inversion in each conformer in compound 1. In the solid state, comparable magnitudes for the stabilization of the stable conformers for the more or less discrete molecules, the polarization effects, hydrogen bonding and the packing effects could be anticipated.

The geometry of compound (1) optimized by density functional calculations at the B3LYP/6-31++G* (d,p) level, is in good agreement with data obtained from X-ray crystallography.     

Synthesis, Dimeric Crystal Structure, and Biological Activities of N- （ 4-Methyl-6-oxo-1,6-dihydro-pyrimidin-2-yl ） -N＇- （ 2-trifluoromethyl-phenyl ） -guanidine

The title compound, N-（4-methyl-6-oxo-1,6-dihydro-pyrimidin-2-yl）-N＇-（2-tritluoromethyl-phenyl）-guanidine, was synthesized and its structure was confirmed by using IR, MS,^1H NMR, and elemental analysis. The single crystal structure of the title compound was determined by X-ray diffraction. The preliminary biological test showed that the synthesized compound has a weak herbicidal activity.     

Structural, spectral and thermal studies of N-2-(4-picolyl)- and N-2-(6-picolyl)-N′-(2-chlorophenyl)thioureas and N-2-(6-picolyl)-N′-(2-bromophenyl)thiourea

N-2-(4-picolyl)-N′-2-chlorophenylthiourea, 4PicTu2Cl, monoclinic, P2₁/c, a=10.068(5), b=11.715(2), β=96.88(4)°, and Z=4; N-2-(6-picolyl)-N′-2-chlorophenylthiourea, 6PicTu2Cl, triclinic, P-1, a=7.4250(8), b=7.5690(16), c=12.664(3) Å, =105.706(17), β=103.181(13), γ=90.063(13)°, V=665.6(2) ų and Z=2 and N-2-(6-picolyl)-N′-2-bromophenylthiourea, 6PicTu2Br, triclinic, P-1, a=7.512(4), b=7.535(6), c=12.575(4) Å, a=103.14(3), β=105.67(3), γ=90.28(4)°, V=665.7(2) ų and Z=2. The intramolecular hydrogen bonding between N′H and the pyridine nitrogen and intermolecular hydrogen bonding involving the thione sulfur and the NH hydrogen, as well as the planarity of the molecules, are affected by the position of the methyl substituent on the pyridine ring. The enthalpies of fusion and melting points of these thioureas are also affected. ¹H NMR studies in CDCl₃ show the NH′ hydrogen resonance considerably downfield from other resonances in their spectra.     

Spectroscopic characterization and single molecule structures of N,N-bis-(3-phthalimidopropyl)-N-(2-hydroxyethyl)-N-propylammonium salts and their hydrates

N,N-Bis-(3-phthalimidopropyl)-N-(2-hydroxyethyl)-N-propylammonium salts and their hydrates have been characterized by FTIR, Raman and NMR spectroscopy. Also B3LYP and PM5 calculations have been carried out. The optimized bond lengths, bond angles and torsion angles calculated by B3LYP/6-31G(d,p) approach have been compared with the spectroscopic data. The screening constants for ¹³C and ¹H atoms have been calculated by the GIAO/B3LYP/6-31G(d,p) approach and analyzed. Linear correlations between the experimental ¹H and ¹³C chemical shifts and the computed screening constants confirm the optimized geometry.     

Synthesis and physico-chemical studies on complexes of 1,2-diaminophenyl-N,N′-bis-(2-pyridinecarboxaldimine), (L): A spectroscopic approach on binding studies of DNA with the copper complex

The Schiff base ligand, 1,2-diaminophenyl-N,N′-bis-(2-pyridinecarboxaldimine), (L) has been synthesized by the reaction of o-phenylenediamine and 2-pyridinecarboxaldehyde, and a series of mononuclear complexes of the type [ML(NO₃)₂] [M = Co(II), Ni(II), Cu(II) and Zn(II)] has also been synthesized. The formation of the Schiff base ligand (L) and its complexes have been envisaged from IR, ¹H and ¹³C NMR studies. The absorption band observed in the electronic spectra and magnetic moment values confirm an octahedral environment around the metal ion. The molar conductivity measurements confirm the non-ionic character of these complexes. Fluorescence and UV–Vis absorption studies performed on the Cu(II) complex revealed a significant binding ability to DNA.     

N,N′-bis(substituted-phenyl)oxamides and their dinuclear pentacoordinate nickel(II) complexes

The preparation, spectroscopic characterization and magnetic study of N,N′-bis(substituted-phenyl)oxamidate-bridged nickel(II) dinuclear complexes of formula {[Ni(N₃-mc)]₂(μ-CONC₆H₄-X)}(PF₆)₂ (N₃-mc = 2,4,4-trimethyl-1,5,9-triazacyclo-dodec-1-ene (Me₃-N₃-mc) or 2,4,4,9-tetramethyl-1,5,9-triazacyclododec-1-ene (Me₄-N₃-mc), X = 2-Cl, 4-Cl, 2-OCH₃, 4-OCH₃) are reported. These paramagnetic nickel(II) complexes have been characterized by both one- and two-dimensional (COSY) ¹H NMR techniques. The COSY spectrum of 5 has allowed to achieve the assignment of the phenyl protons of the N,N′-diphenyloxamidate. The crystal structures of [Ni(Me₃-N₃-mc)(μ-CONC₆H₄-4-Cl)]₂(PF₆)₂ (6), [Ni(Me₃-N₃-mc)(μ-CONC₆H₄-4-OMe)]₂(PF₆)₂ (8) and [Ni(Me₄-N₃-mc)(μ-CONC₆H₄-2-Cl)]₂(PF₆)₂ (9) have been determined and their magnetic properties have been studied. The value of magnetic coupling between the two nickel(II) ions across the oxamidate bridge [J = − 37.6 (6), −39.9 (8) and −39.7 cm⁻¹ (9)] is sensitive to the distortion of the coordination sphere of the metal ions and the topology of the molecular bridge.     

Microstructure determination of N-vinyl-2-pyrrolidone/butyl acrylate copolymers by NMR spectroscopy

The copolymer composition of N-vinyl-2-pyrrolidone/butyl acrylate (V/B) copolymers was determined from the quantitative ¹³C{¹H} NMR spectra. The monomer reactivity ratios for N-vinyl-2-pyrrolidone (V) and butyl acrylate (B) were found to be r_V=0.11±0.07, r_B=0.54±0.19, using the Kelen–Tudos and non-linear least-square error-in-variable (EVM) methods. The ¹³C{¹H} and ¹H NMR spectra of these copolymers are overlapping and complex. The complete spectral assignment of the carbon and proton NMR spectra were done by employing distortionless enhancement by polarization transfer (DEPT) and two-dimensional (2D) ¹³C–¹H heteronuclear single quantum correlation spectroscopy experiments. The 2D total correlation spectroscopy (TOCSY) (¹H–¹H homonuclear TOCSY) NMR spectrum was used to ascertain the various geminal and vicinal couplings in the copolymer.     

Nido-6-metalladecaborane chemistry: Molecular structure and fluxionality of [6,6,6,6-(CO)2(PPh3)2-nido-6-WB9H13]

The molecular and crystal structure of the nido-6-tungstadecaborane [6,6,6,6-(CO)₂(PPh₃)₂-nido-6-WB₉H₁₃] (1) has been determined showing that the tungsten atom is incorporated into the 6-position of a nido 10-vertex (WB₉) cage. The tungsten atom has a seven-coordinate capped trigonal prismatic environment and is bonded to two hydrogen and three boron atoms of the {B₉H₁₃} cage, in addition to two CO groups and two PPh₃ ligands. Variable-temperature (−90°C to +50°C) ³¹P{¹H} NMR spectroscopy of 1 reveals that the exo-polyhedral ligands about the tungsten atom are fluxional with respect to PPh₃ site exchange with an activation energy (ΔG‡), at the coalescence temperature (−73°C), of <38 kJ mol⁻¹.     

Structural and spectral studies on N-(4-chloro)benzoyl-N′-(4-tolyl)thiourea

The crystal and molecular structure of the N-(4-chloro)benzoyl-N′-(4-tolyl)thiourea (C₁₅H₁₃N₂OSCl, M_r=304.79) is determined by X-ray diffraction. The crystal structure is monoclinic, space group: P2₁/n, a=16.097(6), b=4.5989(2), c=19.388(7) Å and β=89.299(6)° V=1434.7(9)ų, Z=4. FTIR and NMR spectra have been characterized. The interactions of intramolecular and intermolecular hydrogen bonds have been discussed. Density functional theory (DFT) (B3LYP) methods have been used to determine the structure and energies of stable conformers. Minimum energy conformations are calculated as a function of the torsion angle θ (C13–N1–C14–N2) varied every 30°. The optimized geometry corresponding to crystal structure is the most stable conformation. This has partly been attributed to intramolecular hydrogen bonds. With the basis sets of the 6-311G* quality, the DFT calculated bond parameters and harmonic vibrations are predicted in a very good agreement with experimental data.     

Synthesis and characterisation of alkyl-N,N′-bis(salicylidene)ethylenediamino- and alkyl-N,N′-bis(salicylidene)-1,2-phenylenediaminogallium or indium complexes: crystal structure of methyl-N,N′-bis(salicylidene)-1,2-phenylenediaminoindium

The reaction of trialkylgallium or indium R₃M (M=In, Ga; R=Me, Et) with N,N′-ethylenebis(salicylideneimine) or 1,2-N,N′-phenylenebis(salicylideneimine) yields seven intramolecularly coordinated organogallium or organoindium complexes. Two hydroxyl protons in the ligands react with both trialkylindium and trimethylgallium, while one hydroxyl group reacts exclusively with triethylgallium. The complexes obtained have been fully characterised by elemental analysis, ¹H-NMR, IR and mass spectroscopy. The structure of methyl-N,N′-bis(salicylidene)-1,2-phenylenediaminoindium (1) has been determined by single-crystal X-ray analysis. The In atom is five coordinate in the structure. Fluorescence spectroscopy has shown that the maximum emission wavelength of 1 is 499 nm upon radiation by UV light.     

Structural and spectral studies of N-2-(pyridyl)-, N-2-(3-, 4-, 5-, and 6-picolyl)- and N-2-(4,6-lutidyl)-N′-2-thiomethoxyphenylthioureas

Structures of the following compounds have been obtained: N-(2-pyridyl)-N′-2-thiomethoxyphenylthiourea, PyTu2SMe, monoclinic, P2₁/c, a=11.905(3), b=4.7660(8), c=23,532(6) Å, β=95.993(8)°, V=1327.9(5) ų and Z=4; N-2-(3-picolyl)-N′-2-thiomethoxyphenyl-thiourea, 3PicTu2SeMe, monoclinic, C2/c, a=22.870(5), b=7.564(1), c=16.941(4) Å, β=98.300(6)°, V=2899.9(9) ų and Z=8; N-2-(4-picolyl)-N′-2-thiomethoxyphenylthiourea, 4PicTu2SMe, monoclinic P2₁/a, a=9.44(5), b=18.18(7), c=8.376(12) Å, β=91.62(5)°, V=1437(1) ų and Z=4; N-2-(5-picolyl)-N′-2-thiomethoxyphenylthiourea, 5PicTu2SMe, monoclinic, C2/c, a=21.807(2), b=7.5940(9), c=17.500(2) Å, β=93.267(6)°, V=2893.3(5) ų and Z=8; N-2-(6-picolyl)-N′-2-thiomethoxyphenylthiourea, 6PicTu2SMe, monoclinic, P2₁/c, a=8.499(4), b=7.819(2), c=22.291(8) Å, β=90.73(3)°, V=1481.2(9) ų and Z=4 and N-2-(4,6-lutidyl)-N′-2-thiomethoxyphenyl-thiourea, 4,6LutTu2SMe, monoclinic, P2₁/c, a=11.621(1), b=9.324(1), c=14.604(1) Å, β=96.378(4)°, V=1572.4(2) ų and Z=4. Comparisons with other N-2-pyridyl-N′-arylthioureas having substituents in the 2-position of the aryl ring are included.     

Infrared and Raman spectra of 2-chloro-2,2-difluoroacetamide (ClF2CC(O)NH2)

The infrared and Raman spectra of 2-chloro-2,2-difluoroacetamide (ClF₂CC(O)NH₂) have been recorded and analyzed with the complement of results derived from computational chemistry calculations. Thus, delocalization effects and stabilization energies have been computed for the title molecule and a complete assignment has been also proposed. ¹³C, ¹⁹F and ¹H NMR chemical shifts and coupling constants have been also measured for this substance.     

The reaction of (μ-H)2Os3(CO)9(PPh3) with ethylene affords the ethylidene complex (μ-H)2Os3(CO)9(PPh3)(μ-CHCH3)

The product isolated from the reaction of (μ-H)₂Os₃(CO)₉(PPh₃) with ethylene is shown to be the ethylidene complex (μ-H)₂Os₃(CO)₉(PPh₃)(μ-CHCH₃) (1) rather than the ethylene complex (μ-H)(H)Os₃(CO)₉(PPh₃)(C₂H₄), as previously claimed. The characterization of 1 is based on a combination of ¹H and ¹³C NMR results. The ¹H NMR data (δ 6.84 (1 H_D), 2.53 (3 H_C), J(CD) = 7.4 Hz) establish the presence of the ethylidene moiety, whereas detailed analysis of the 1-D and 2-D ¹³C NMR spectra of ¹³CO-enriched 1 indicates the relative positions of the ethylidene, hydride, and phosphine ligands on the triosmium framework.     

Ab initio study of 1,1-(methylphosphinylidene) bis(methanamine) and vibrational assignment of its N,N′-coordinated Pt(II) and Pd(II) chloro complexes

Infrared and Raman spectra of 1,1-(methylphosphinylidene) bis(methanamine) [mpbm, (CH₃)PO(CH₂NH₂)₂] and its N,N′-coordinated Pt(II) and Pd(II) have been studied in the 4000–200 cm⁻¹ frequency range. Ab initio calculations have been carried out for different conformations of the mpbm at HF/6-31G* level of the theory from which structural parameters, conformational stability and predicted infrared and Raman spectra have been obtained. A complete vibrational assignment of the lowest energy conformer, tttg⁻, as well as of its N,N′-coordinated Pt(II) and Pd(II) chloro-complexes was done on the basis of the calculated frequencies, relative infrared intensities, Raman activities and potential energy distribution (PED). The theoretical predictions are compared with the experimental results where appropriate.     

Synthesis, spectroscopic studies and nonlinear optical behavior of N,N′-bis(2-hydroxy-1-naphthylmethylidene)-1-methyl-1,2-diaminoethane-N,N′,O,O′-nickel(II)

A Schiff base complex N,N′-bis(2-hydroxy-1-naphthylmethylidene)-1-methyl-1,2- diaminoethane-N,N′,O,O′-nickel(II) has been synthesized. The title compound has been characterized by FT-IR and UV–vis spectroscopies. The UV–vis experiments indicate that the compound has solvatochromism in the UV region, implying non-zero molecular first hyperpolarizability. To investigate microscopic second-order nonlinear optical (NLO) behavior of the examined complex, the electric dipole moments (μ) and the first static hyperpolarizabilities (β) were computed using Finite Field second-order Møller Plesset (FF MP2) perturbation procedure. According to ab initio quantum mechanical calculations, the title complex exhibits non-zero β values, revealing microscopic second-order NLO behavior.     

A homodinuclear complex of manganese containing novel ligand, Mn2(CO)6(μ-H){μ-S(SC3H5)C=C(PPr3)S}

The title complex Mn₂(CO)₆(μ-H){μ-S(SC₃H₅)C=C(PPr₃ⁱ)S} was synthesized by allyation of the homobinuclear anion [Mn₂(CO)₆(μ-H){μ-S(SC₃H₅)C=C(PPr₃ⁱ)S}]⁻¹, and characterized by elemental analysis, IR, ¹H NMR and ³¹P NMR spectra. The molecular structure shows that it contains a novel fairly planar ligand S(S)C=C(PPr₃ⁱ)S, and the two Mn(CO)₃ fragments are symmetrically placed at both sides of the plane of the ligand.     

Synthesis and characterization of two tris-chelate complexes of cobalt(III) with 3,5-dimethyl-1-(N-methyl/ethyl)thiocarbamylpyrazole (HL1, HL2) — biologically important bidentate ligands with one ambidentate donor site

Cobalt(III) complexes, of two potentially pyrazole-derived bidentate ligands (with one ambidentate donor site), 3,5-dimethyl-1-(N-methyl/ethyl)thiocarbamylpyrazole (HL₁ for N-methyl, HL₂ for N-ethyl) have been synthesized and characterized by elemental analyses, IR, UV–Vis and ¹H NMR spectral studies. The structure of Co(L₂)₃ has been determined by single-crystal X-ray diffraction studies. The complex (triclinic, space group P ) has a distorted octahedral structure with the ambidentate ligands coordinated to the Co(III) ion as uninegative bidentate chelating agents via the pyrazole ring nitrogen (tertiary) and the thiocarbamyl iminyl nitrogen atoms. The distortion from the regular octahedral geometry is ascribed to the stereochemical limitations imposed by the planar bidentate ligands.     

New N′-alkylidene/cycloalkylidene derivatives of 5-methyl-3-phenyl-1H-indole-2-carbohydrazide: synthesis, crystal structure, and quantum mechanical calculations

The condensation products of 5-methyl-3-phenyl-1H-indole-2-carbohydrazide (1) with 2-butanone, 3-pentanone and cyclopentanone were prepared. The adducts (2a-c) were characterized by microanalysis, UV, IR, ¹H NMR, ¹³C NMR and EI mass spectrometry. ¹H NMR spectra of 2a and 2b revealed rotational restriction about the C–N bond in solution (DMSO-d₆) and displayed double resonances associated with the CH₃ and CH₂CH₃ residues of the alkylidene moieties. A variable temperature ¹H NMR experiment was run on 2a to overcome the rotational barriers and thus determine the coalescence temperature but no coalescence was observed up to 77 °C. The structural analysis of 2a and 2c were also carried out by single crystal X-ray diffraction and confirmed by theoretical calculations (semiempirical PM3 and ab initio RHF/6-31G(d)).     

Synthesis of N,N′-dimethyl-N,N′-dibutyl malonamide functionalized polymer and its sorption affinities towards U(VI) and Th(IV) ions

A novel chelating polymeric material was synthesized by chemical anchoring of N,N′-dimethyl-N,N′-dibutyl malonamide (DMDBMA) with chloromethylated polystyrene-divinyl benzene polymer. The polymeric material thus prepared was characterized by ¹³C NMR, FT-IR spectroscopy and CHN elemental analysis. The fabricated polymeric material exhibited superior binding for hexa-valent and tetra-valent metal ions such as U(VI) and Th(IV). Various physico-chemical properties of the functionalized polymer like phase adsorption kinetics, metal sorption mechanism and metal sorption capacity was studied in the static method. Adsorption kinetics studies show that <20 min was sufficient for >99.99% adsorption of Th(IV) and U(VI). The kinetics for adsorption of U(VI) and Th(IV) was found to follow the first order Lagergren rate kinetics. Adsorption of U(VI) on the malonamide functionalized polymer followed the Langmuir adsorption isotherm. The Langmuir monolayer adsorption phenomenon was also confirmed by the theoretical approach calculated based on the adsorption kinetics. The metal sorption capacities for uranium and thorium were found to be 18.78 ± 1.53 mg and 15.74 ± 1.59 mg/g of the chelating polymer at 3 M HNO₃, respectively.     

NMR spectra of salicylohydroxamic acid in DMSO-d6 solution: a DFT study

The ¹H, ¹³C and ¹H, ¹³C COSY NMR spectra of salicylohydroxamic acid (sha) were measured in DMSO-d₆ solution. The B3LYP GIAO method with the 6-311++G(d,p) basis set was chosen to reproduce the experimental spectra. All possible zusammen and entgegen conformers of monomeric sha were computed. After geometry optimisation (B3LYP/6-311++G(d,p)) only nine independent models of the molecule were shown to be stable. Additionally, the NMR chemical shifts of the Onsager model of the most stable monomer were calculated. The computed chemical shifts for the labile protons for all aforementioned geometries meaningfully underestimated experimental results suggesting the existence of the H-bonded structure of sha in DMSO solution. The most probable two dimeric structures along with two solvent-bounded aggregates were subsequently calculated at the same level of theory. The best agreement was obtained for sha H-bonded with two DMSO molecules (confirmed by the absence of concentration effect). The relative error not exceeding 10 and 4% for chemical shifts in ¹H and ¹³C NMR spectra of sha–(DMSO)₂, respectively, showed that the applied method with the B3LYP/6-311++G(d,p) basis set was efficient to predict the NMR shifts of a compound with strong H-bonds. Thus, this allows to assign properly NMR resonances to specific structure formed in DMSO solution.