M. Venter

FT-Raman studies on new triphenylphosphin-copper(I) triazenido complexes

Abstract The reaction of neutral triazenides HL, L= p -XC 6 H 4 NNNC 6 H 4 Y- p , X=Y=CH 3 (1), C 2 H 5 (2), and X=CH 3 , Y=H (3), with [(PPh 3 ) 2 Cu(CH 3 COO)] 2 , Ph = C 6 H 5 in boiling methanol yields new triphenylphosphin-copper I ) triazenido complexes: [(PPh 3 )CuL] 2 , X = Y = CH 3 ( 1′ ), and [(PPh 3 ) 2 CuL], X = Y = C 2 H 5 ( 2′ ) and X = CH 3 , Y = H ( 3′ ). The Raman spectra of the protonated ligand ( 1–3 ) and the new corresponding Cu(I) complexes ( 1′–3′ ) are discussed in comparison. The observed changes in position and band intensities of the FT-Raman spectra confirm the coordination of deprotonated triazenido ligand to the Cu(I) centers.

IR and ESR study of Cu(II)-nitrazepam complexes

Abstract The CuL 2 X 2 (L = 7-nitro-1,3-dihydro-5-phenyl-2 H -1,4-benzodiazepin-2-one, known as nitrazepam, X = Cl, Br) complexes were prepared and investigated by IR, ESR and magnetic susceptibility measurements. The IR spectra suggest that the Cu(II) ion is coordinated by two nitrogen and two halogen atoms. The powder ESR spectrum at room temperature of CuL 2 Br 2 is quasiisotropic, while that of CuL 2 Cl 2 is characteristic of an axial monomeric species with small rhombic distortions. The isotropic ESR spectra of these compounds in DMF and Py solutions suggest the presence of pseudo-tetrahedral monomeric species. Two different monomeric species were evidenced in Cu(II)-nitrazepam solutions adsorbed onto NaY zeolite.

IR AND ESR STUDIES ON NEW BIS-TRIAZENIDO COBALT(II) AND COPPER(II) COMPLEXES

Abstract The reaction of Co(OAc) 2 ·4H 2 O and Cu(OAc) 2 ·H 2 O with new bis-triazenido proligands, H 2 L, L = CH 2 (C 6 H 4 NNNC 6 H 4 ue5f8Xue5f8p − ) 2 X = Meue5f8 ( a ), MeOue5f8 ( b ), in methanol acetone yields binuclear complexes [ML] 2 , M = Co 2+ ( 1a, b ) and Cu 2+ ( 2a, b ), as green noncrystalline solids. The IR spectra present the three typical vibrations ( v as , v s and δ) of the deprotonated triazenido unit (NNN) according to the C 2v symmetry. The ESR characterisation proves the N 1 N 3 ue5f8 η 2 , N 4 N 6 ue5f8 η 2 tetraconnective bis-chelating coordination of bis-triazenido anions and the square-planar symmetry of the MN 4 chromophore. For the cobalt(II) complexes a small rhombic distortion can be mentioned.

Vibrational Behavior of Transition Metal Cupferronato Complexes: Raman Studies on Cobalt(II) Cupferronato Derivatives

Abstract The FT-Raman spectrum of cupferron, [PhN2O2]NH4 and the micro-Raman spectra of the new corresponding cobalt(II) cupferronato complexes, CoL2A2, L = PhN2O2, a = H2O, MeOH, o-C6H4(NH2)2, p-C6H4(NH2)2 and CoL2A, a = (-C6H4NH2-p)2 were recorded and discussed. All the complexes show a Raman band at about 1302 cm1 and the characteristic v(N-N) and δ(ONNO) modes of the anionic ligand. the vibrational analysis of the title compounds reveals the electron delocalisation over the N-nitroso-N-hydroxylaminato (ONNO) unit, as well as the bidentate coordination of the cupferronato ligand to the metal center through the oxygen atoms.

SERS application in elucidation of the nature of homologue Cu(I) triazenido complexes

Abstract The reaction of the neutral 1,3-diphenyltriazenide derivative PhNHNNPh with [(PPh 3 ) 2 Cu(CH 3 COO)] 2 leads to a mixture of different coordinated Cu(I) complexes (TPPC), in contrast to the homologue complexes containing bidentate triazenido ligands, [(PPh 3 )Cu(TolNNNTol)] 2 and [(PPh 3 ) 2 Cu(XC 6 H 4 NNNC 6 H 4 Y)], X=Y=Et, X=H, Y=Me. The SERS spectrum of the reaction product reveals the strong enhancement of the ν (Nue605N) mode, characteristic to the monodentate ligand, in contrast to the commonly enhanced band ν s (NNN) of the related studied complexes with bidentate triazenido ligands. The complete analysis of the SERS spectrum elucidates the nature of the mixed Cu(I) triazenido complexes in the reaction product and strongly suggests the presence of the main complex, with monodentate coordinated Cu(I), adsorbed on the Ag surface.

Vibrational and orientation studies of 2,4-diamino-6-phenyl-1,3,5-triazine on a colloidal silver surface

Abstract The Raman, IR and SERS spectra of 2,4-diamino-6-phenyl-1,3,5-triazine (DPT) have been recorded. One protonated form of the DPT molecule was evidenced. The DPT molecule was found to adsorb on to a silver colloidal surface in either the neutral or the protonated form. Vibrational assignments are proposed for DPT and the DPT ion. Comparison of the Raman spectra of DPT and the DPT ion in solution with the SERS spectra results in an orientation with the triazinic skeletal DPT plane perpendicular on the Ag surface. The same orientation with more or less tilt was found for the adsorbed DPT ion.

Lipophilic marine biotoxins SERS sensing in solutions and in mussel tissue

To detect and recognise three structurally related marine biotoxins responsible for the diarrheic shellfish poisoning (DSP) symptom, namely okadaic acid (OA), dinophysistoxin-1 (DTX-1) and dinophysistoxin-2 (DTX-2) respectively, as well as the structurally different yessotoxin (YTX), we developed a novel surface-enhanced micro-Raman scattering (micro-SERS) approach to investigate for the first time their micro-SERS signalling in solution and jointly analysed them in conjunction with the normal and toxic mussel tissue. YTX provided the main SERS feature surprisingly similar to DTX-1 and DTX-2, suggesting similar molecular adsorption mechanism with respect to the AgNPs. A fingerprint SERS band at 1017u202fcm-1 characteristic for the C-CH3 stretching in DTX-1 and DTX-2 and absent in OA SERS signal, allowed direct SERS discrimination of DTX-1,2 from OA. In acid form or as dissolved potassium salt, OA showed reproducible SERS feature for 0.81u202fμM to 84.6u202fnM concentrations respectively, while its ammonium salt slightly changed the overall SERS signature. The inherently strong fluorescence of the shellfish tissue, which hampers Raman spectroscopy analysis, further increases when toxins are present in tissue. Through SERS, tissue fluorescence is partially quenched. Artificially intoxicated mussel tissue with DSP toxins and incubated with AgNPs allowed direct SERS evidence of the toxin presence, opening a novel avenue for the in situ shellfish tracking and warning via micro-SERS. Natural toxic tissue containing 57.91u202fμgu202fkg-1 YTX (LC-MS confirmed) was micro-SERS assessed to validate the new algorithm for toxins detection. We showed that a portable Raman system was able to reproduce the lab-based SERS results, being suitable for in situ raw seafood screening. The new approach provides an attractive, faster, effective and low-cost alternative for seafood screening, with economic, touristic and sustainable impact in aquaculture, fisheries, seafood industry and consumer trust.