Solid-state Linear-dichroic Infrared Research Articles

New Au (III), Pt (II) and Pd (II) Complexes with Pentapeptide Glycylglycyl-L-Methyonyl-Glycyl-Glycine and Their Interaction with Calf Thymus DNA

The three new Au (III), Pt (II) and Pd (II) complexes with pentapeptide glycyl-glycyl-(L)-methyonyl-glycyl-glycine have been synthesized, isolated, and spectroscopically and structurally elucidated in solution and in the solid-state. Solid-state linear-dichroic infrared (IR-LD) spectroscopy of oriented colloids in a nematic liquid crystal host, (1)H- and (13)C-NMR, TGA and DSC, UV-VIS spectroscopy, EPR, ESI- and FAB- mass spectrometry and HPLC tandem mass spectrometry (HPLC-MS/MS) have been used. Quantum chemical calculations and molecular modelling were carried out in order to determine the structures and spectroscopic properties of the ligand, the newly synthesised metal complexes and their interactions with calf thymus DNA. The pentapeptide coordinates in a tetradentate manner with the metal ions via an S-atom on the methyonyl-side chain, two N-amide nitrogens, (after a deprotonation of gly(1) and gly(2) residues) and the primary NH(2) nitrogen of N(termini). The MN(3)S chromophores are distorted to near square planar geometry. Their interaction with calf thymus DNA shows the competitive N7 (G) coordination position, where the pentapeptide residues is coordinated with the metal centers in a tridentate manner through the S-atom and both N-amide centers. This interaction leads to a transfer from a distorted square planar geometry (D(4h) symmetry) to a pseudo tetrahedral (T(d) symmetry) of the metal ions with the obtained dihedral angle values of the MN(3)N7(G) chromophors within 114.67 degrees to 110.92 degrees . The isolated Au (III) complex is stable for about 1.5 months, while the stability of the Au (III) complex/DNA adduct is decreased to 33 days.

New Au(III), Pt(II) and Pd(II) complexes with glycyl-containing homopeptides

Twelve new Au(III), Pt(II) and Pd(II) complexes with glycyl-containing homopeptides glycyl-glycine (G2), glycyl-glycyl-glycine (G3), glycyl-glycyl-gycyl-glycine (G4), glycyl-glycyl-glycyl-glycyl-glycine (G5) and glycyl-glycyl-glycyl-glycyl-glycyl-glycine (G6) have been synthesized, isolated and characterized spectroscopically and structurally by means of solid-state linear-dichroic infrared (IR-LD) spectroscopy of oriented colloids in nematic liquid crystal host, 1H- and 13C-NMR, TGA and DSC, UV–Vis spectroscopy, EPR, ESI- and FAB mass spectrometry and HPLC tandem mass spectrometry (HPLC-MS/MS). Quantum chemical calculations are carried out with a view to obtain the structures and spectroscopic properties of the ligand and newly synthesized metal complexes.

Determination of cephalosporins in solid binary mixtures by polarized IR- and Raman spectroscopy

Quantitative IR- and Raman spectroscopic determinations of four cephalosporin antibiotics in six solid binary mixtures have been conducted. This is a new approach for spectroscopic determination of these antibiotics, since the corresponding quantitative analysis in solution only has been reported so far. The correlation coefficient r 2 was found to be in the confidence intervals within 99.32–99.88% and 99.90–95.54% for the systems under study by using the absorption ratios of the characteristic bands at 800 cm −1 and 721 cm −1 present in the IR- and Raman spectra of the antibiotic compounds cephalexin, cephalotin, cephaloglycin and cephamandole, respectively. Solid-state linear dichroic infrared (IR-LD) spectral analysis of the solid mixtures was carried out in order to obtain experimental IR-spectroscopic assignment of the compounds studied. Independent high-performance liquid chromatography–tandem mass spectrometry (HPLC–MS/MS) analysis was performed for the validation of the vibrational spectroscopic data. The application of this instrumental analytical tool for the analysis of 10 tablets of the commercial products Cefamandole and Cefalotin (Actavis) was also studied.

Determination of phenacetin and salophen analgetics in solid binary mixtures with caffeine by infrared linear dichroic and Raman spectroscopy

Quantitative infrared (IR) and Raman spectroscopic approach for determination of phenacetin ( Phen) and salophen ( Salo) in binary solid mixtures with caffeine: phenacetin/caffeine ( System 1) and salophen/caffeine ( System 2) is presented. Absorbance ratios of 746 cm −1 or 721 cm −1 peaks (characteristic for each of determined compounds in the Systems 1 and 2) to 1509 cm −1 and 1616 cm −1 (attributed to Phen and Salo, respectively) were used. The IR spectroscopy gives confidence of 98.9% ( System 1) and 98.3% ( System 2), while the Raman spectroscopic data are with slightly higher confidence of 99.1% for both systems. The limits of detection for the compounds studied were 0.013 and 0.012 mole fraction for IR and Raman methods, respectively. Solid-state linear dichroic infrared (IR-LD) spectral analysis of solid mixtures was carried out with a view to obtaining experimental IR spectroscopic assignment of the characteristic IR bands of both determined compounds. The orientation technique as a nematic liquid crystal suspension was used, combined with the so-called reducing-difference procedure for polarized spectra interpretation. The possibility for obtaining supramolecular stereo structural information for Phen and Salo by comparing spectroscopic and crystallographic data has also been shown. An independent high-performance liquid chromatography–tandem mass spectrometry (HPLC–MS/MS) analysis was performed for comparison and validation of vibrational spectroscopy data. Applications to 10 tablets of commercial products APC and Sedalgin are given.

Aromatic dipeptides and their salts—Solid-state linear-dichroic infrared (IR-LD) spectral analysis and ab initio calculations

Stereo-structural analysis and IR-bands assignment of the aromatic dipeptides l-tryrosyl- l-phenylalanine ( Tyr-Phe), l-phenylalanyl- l-tyrosine ( Phe-Tyr) and their hydrochloride salts have been carried out by means of IR-LD spectroscopy of oriented as nematic liquid crystal suspension solid samples. The experimental data are compared with known crystallographic ones and theoretical predicted geometries at RHF/ and UHF/6-31G**.

Spectroscopic and structural elucidation of alanyl-containing dipeptides and their hydrogensquarates

The hydrogensquarates of alanyl-containing dipeptides glycylalanine ( H-Gly-Ala-OH) and alanylalanine ( H-Ala-Ala-OH) are characterized structurally by means of quantum chemical ab initio calculations, solid-state linear-dichroic infrared (IR-LD) spectroscopy, 1H and 13C NMR data, ESI-MS, HPLC-MS/MS, TGV and DSC methods. The structures consist in positive charged peptide moiety and negative hydrogensquarate anion (HSq −), stabilizing by strong intermolecular hydrogen bonds. The theoretical and IR-LD spectroscopic data are compared with corresponding ones of zwitterion dipeptides with a view to understanding the structural and conformational changes as well as the IR-spectroscopic ones as a result of hydrogensquarates formation. The strong overlapped and complicated IR-spectroscopic bands typical for hydrogensquarates in solid-state are assigned supporting with the presented vibrational analysis of the dipeptides and of the hydrogensqauarate anion.

Spectroscopic and structural elucidation of l-tyrosine-containing dipeptides valyl-tyrosine and tyrosyl-alanine: Solid-state IR-LD spectroscopy, quantum chemical calculations and vibrational analysis

l-Tyrosine-containing dipeptides valyl-tyrosine ( H-Val-Tyr-OH) and tyrosyl-alanine ( H-Tyr-Ala-OH) are characterized structurally by means of quantum chemical ab initio calculations and solid-state linear-dichroic infrared (IR-LD) spectroscopy. The IR-characteristic bands are assigned by application of reducing-difference procedure for polarized IR-spectra interpretation. Infrared data obtained are supported as well by the made vibrational analysis. The structures of both peptides are predicted on the basis of conformational analysis and structural information, obtained by the shown IR-spectroscopic tool.

Spectral analysis and crystal structure of a new mononuclear copper(II) complex of 3-aminopyridine

A new Cu(II)-complex of 3-aminopyridine, [CuCl(3-AP)4][Cu(3-AP)4(H2O)]Cl3 · 2H2O (1), containing two contrasting complex cations has been synthesized and structurally characterized by single crystal X-ray diffraction and solid-state linear-dichroic infrared (IR-LD) spectral analysis. In both cations four 3-AP molecules coordinate the Cu(II) atom in a monodentate fashion through their endocyclic (Npy) nitrogens, thereby generating a square-planar coordination geometry for the CuN4 chromophor. Perpendicular to the N4 plane, the metal ion is coordinated by a chloride anion in the first cation and a water ligand in the second cation. One of three additional water molecules of crystallization occupies the vacant octahedral site of the second cation and participates in a weak Cu···OH2 interaction. An IR-LD spectral analysis of the samples, oriented as a suspension in a nematic liquid crystal confirmed the crystallographic data and the retention of the pyridine ring aromatic character after coordination. The presented results are additionally supported by UV, 1H-NMR, EPR and MS analysis and by thermogravimetric and calorimetric data.

The dipeptide alanylphenylalanine ( H-Ala-Phe-OH) – protonation and coordination ability with Au(III)

The dipeptide alanylphenylalanine ( H-Ala-Phe-OH), its hydrochloride ( HCl × H-Ala-Phe-OH) and Au(III)-complex have been characterized structurally. Quantum chemical DFT and ab initio calculations, solid-state linear-dichroic infrared (IR-LD) spectroscopy and 1H and 13C NMR data were employed. The results are confirmed by a single crystal X-ray diffraction analysis of HCl × H-Ala-Phe-OH. The coordination with Au(III) is supported by data from MS, TGV, DSC methods and by elemental analysis. The H-Ala-Phe-OH coordinates in a bidentate manner via an O-atom of the COO −-group and N-amide nitrogen, after a previous deprotonation of the NH-group has taken place. Two Cl − ions are attached to the metal center as terminal ligands, yielding a completely planar geometry for the AuNOCl 2 chromophor in the mononuclear [Au(( H-Ala-Phe-OH)H −1)Cl 2] complex.

Structural and spectroscopic analysis of hydrogensquarates of glycine‐containing tripeptides

The hydrogensquarates of glycine-containing tripeptides glycylglycylglycine (H-Gly-Gly-Gly-OH), glycylglycylmethionine (H-Gly-Gly-Met-OH), and methionylglycylglycine (H-Met-Gly-Gly-OH) have been characterized structurally. Quantum chemical ab initio calculations, solid-state linear-dichroic infrared (IR-LD) spectroscopy, 1H and 13C NMR data, ESI-MS, HPLC-MS/MS, TGV, and DSC methods were employed. The structures consist in a positively charged peptide moiety and a negative hydrogensquarate anion (HSq), stabilized by strong intermolecular hydrogen bonds.

Polymorphs of Aspirin – Solid-state IR-LD spectroscopic and quantitative determination in solid mixtures

Solid-state linear-dichroic infrared (IR-LD) spectroscopy, using an orientation technique as a suspension in nematic liquid crystal, has been carried out of Aspirin polymorphs (forms I and II). Reducing-difference procedure for polarized IR-spectra interpretation has been applied for structural analysis of both modifications and the data have been compared with known crystallographic ones. A vibration assignment of forms I and II has been included and on this basis, a quantitative determination by FT-IR spectra for form I in mixtures with second one has been presented, using intensity ratio of 1606 cm −1 peak (characteristic for both forms) to 599 cm −1 one (attributed to form I). The obtained reliability is 99.78%.

Solid state linear-dichroic infrared (IR-LD) spectroscopic characterization of α-and β-glycine polymorphs

AbstractIR-LD spectroscopic analysis using nematic liquid crystal suspension as a solid-state orientation technique and the reducing-difference procedure for polarized spectra interpretation are applied to the α-and β-polymorphs of glycine. Both structural analysis and detailed IR band assignments were carried out.

IR-LD spectroscopic characterization of l-Tryptophan containing dipeptides

IR-spectroscopic and stereo-structural analysis of aromatic l-Tryptophan containing dipeptides l-Tryptophan– l-Tryptophan (Trp–Trp), l-Tyrosine– l-Tryptophan (Tyr–Trp) and cyclo(Trp–Trp) have been carried out by means of solid-state linear-dichroic infrared (IR-LD) spectroscopy of oriented as suspension in nematic liquid crystal solids. The experimental data have been compared with analogous ones of the simple amino acids l-Tyrosnine ( l-Tyr) and l-Tryptophan ( l-Trp). In cyclo(Trp–Trp), the IR-spectral changes towards the IR-ones of acyclic Trp–Trp have been determined. A theoretical analysis of Tyr–Trp at Hartree–Fock level of theory and 6-31G** basis set is also applied.

Stereo-structural and IR-spectral characterization of histidine containing dipeptides by means of solid-state IR-LD spectroscopy and ab initio calculations

By means of solid-state linear-dichroic infrared (IR-LD) spectroscopy the stereo-structures of dipeptides methionyl-histidine (Met-His) and histidyl-methionine (His-Met) are predicted, accompanied with a detailed experimental IR-characteristic bands assignment. The experimental results are compared and confirmed with theoretical structural ones, obtained by ab initio calculations at the Hartree–Fock level of theory and 6-31G**.

Solid-state linear-dichroic infrared spectroscopic analysis of the dipeptide S-Phe–S-Phe and its mononuclear Au(III) complex

Interaction between the S-Phe–S-Phe dipeptide (PP) and Au(III) leads to the formation of a yellow complex, [Au(PP)Cl3]Cl (1), with monodentate coordination of the dipeptide with Au(III) through one O atom of the COO− group. Three Cl− anions bond to the metal center as terminal ligands. The structure of 1 was obtained by comparative solid-state linear-dichroic infrared (LD-IR) spectroscopic analysis of a solid sample and the pure dipeptide S-Phe–S-Phe, both oriented in a nematic liquid crystal suspension.

Monoclinic and orthorhombic polymorphs of paracetamol—solid state linear dichroic infrared spectral analysis

Solid-state linear dichroic infrared (IR-LD) spectral analysis of both monoclinic (form I) and orthorhombic (form II) polymorphs of paracetamol was carried out using an orientation technique as a nematic liquid crystal suspension. The so-called reducing-difference procedure for polarized spectra interpretation was applied and the obtained supramolecular stereo structural data of both modifications were compared with known crystallographic ones. A detailed vibration assignment of characteristic frequencies of forms I and II was also applied. A quantitative FT-IR spectral approach for monoclinic form determination in mixtures by the intensity ratio of 1610 cm −1 peak (characteristic for both forms) to 1666 cm −1 one (attributed to orthorhombic modification) was presented, as well.