Vibrational and electronic studies on interactions of Cu (II) with protic amides: Structural aspects of biological importance

A purely vibrational insight on the tetragonal distortion of [Cu(DMF)6]2+

“…This result as combined to the changes exhibited at the r methyl and d OCN regions allow us to realize that Cu(II) is surrounded by six DMF molecules in an octahedral arrangement, where likely two molecules along the axial axis are more weakly bound to the metal as compared to the others at the equatorial plane, owing to the Jahn-Teller effect. Our interpretation seems to be pertinent since only a new band has been observed either at the m CN region or at the d OCN mode of N-methylformamide (NMF) in the presence of this salt [10]. In that work, a solvation number equal to four was determined and is in excellent agreement with the formation of equivalent bonds at the equatorial plane.…”

“…More recently, we have reported that the shifts observed for the m CO and m CN modes of simple protic amides may be used to indicate what sites are involved in the coordination to the metal [6][7][8][9][10]. So far, the shifts have confirmed the catalytic activity of some metal ions (Zn, Ni and Cu(II)) and may be useful in the prediction of others toward hydrolysis reactions.…”

“…In this way, such parameter has been calculated from the resolved Raman spectra at the r methyl region following the equation [9,10,18,19] . This result as combined to the changes exhibited at the r methyl and d OCN regions allow us to realize that Cu(II) is surrounded by six DMF molecules in an octahedral arrangement, where likely two molecules along the axial axis are more weakly bound to the metal as compared to the others at the equatorial plane, owing to the Jahn-Teller effect.…”

“…Vibrational spectroscopy has been employed by our research group for a long time aiming at describing the solvation structures in metal-amide interaction processes [1][2][3][4][5][6][7][8][9][10]. More recently, we have reported that the shifts observed for the m CO and m CN modes of simple protic amides may be used to indicate what sites are involved in the coordination to the metal [6][7][8][9][10].…”

New Vibrational Information on Simple Amides in Solution: A Case Study on GaCl3-Formamide Complexes

“…On the contrary, FeCl 3 -FA solutions show the arising of the 332 cm − 1 band, which is due to A 1 vibration of [FeCl 4 ] − [8]. In common, the addition of Al 3+ and Fe 3+ chlorides to the FA solvent causes upshifts of both ] CO and ] CN modes, instead of the behavior typically observed as simple amides coordinate other ions and produce the ] CO downshift and the ] CN upshift [8][9][10][11][12][13][14][15]. So far, we have observed that the two spectral patterns of FA show good relationship with the electrostatic potential of coordinated ions, ϕ, and with the catalytic activity of metals toward amide bond cleavage reactions [15].…”