DFT modeling, UV-Vis and IR spectroscopic study of acetylacetone-modified zirconia sol-gel materials

Abstract

Theoretical and spectroscopic studies of a series of monomeric and dimeric complexes formed through the modification of a zirconium butoxide precursor with acetylacetone and subsequent hydrolysis and/or condensation have been performed by applying DFT/B3LYP/6-31++G(d) and highly accurate RI-ADC(2) methods as well as IR and UV-Vis transmittance and diffuse reflectance spectroscopies. Based on DFT model calculations and simulated and experimental UV-Vis and IR spectra of all the studied structures, the most probable building units of the Zr(IV)-AcAc gel were predicted: the dimeric double hydroxo-bridged complex Zr(2)(AcAc)(2)(OH)(4)(OH)(2br) 9 and the monooxo-bridged complex Zr(2)(AcAc)(2)(OH)(4)O(br)·2H(2)O 12. In both structures, the two AcAc ligands are coordinated to one Zr atom. It was shown that building units 9 and 12 determine the photophysical and vibrational properties of the gel material. The observed UV-Vis and IR spectra of Zr(IV)-AcAc gel were interpreted and a relation between the spectroscopic and structural data was derived. The observed UV-Vis bands at 315 nm and 298/288 nm were assigned to partial ligand-metal transitions and to intra-/inter-AcAc ligand transitions, respectively.

Sol–gel hybrid materials for aerospace applications: Chemical characterization and comparative investigation of the magnetic properties

“…Moreover, a strong sharp peak at 1380 cm -1 , due to residual nitrate anions [55], a broad intense band at 3440 cm -1 and the peak at are attributed to C-C vibrations, the peak at 1425 cm -1 is due to methyl C-H symmetric bending [58], whereas the bands at 1026 and 931 cm -1 are assigned to the C-C-H bending mixed with stretching C-C vibrations of AcAc [56]. The bands placed at 654 and 460 cm -1 are due to Zr-OH and Zr-O-Zr stretching respectively [59], whereas the peak at 422 cm -1 to Zr-OAcAc vibrations [56].…”

“…shows the FTIR spectra of ZrO 2 gel (curve a) and pure PCL (curve f) compared with those of the ZrO 2 /PCL hybrid systems (from curve b to e).In the ZrO 2 spectrum (curve a) all typical peaks of AcAc-containing zirconia sol-gel materials[56] are present. The broad intense band at 3417 cm -1 is due to -OH vibrations.…”

“…The position and the shape of the latter bands suggest the presence of hydrogen-bonded solvent molecules (H 2 O) and hydrogen-bonded OH groups attached to the Si atoms[56].In the PEG spectrum (curve f) methylene C-H asymmetric stretching and bending bands are visible at 2870 cm -1 and 1454 cm -1 respectively[57], together with the peaks assigned to terminal C-OH and ethereal C-O stretching at 1250 and 1104 cm -1 respectively and with a little peak at 948 cm -1 attributed to C-C stretching.The SiO 2 /PEG hybrid materials spectra (from curve b to e) show all typical signals of SiO 2 and some polymer picks whose intensity increases with the PEG amount. In particular, the PEG methylene C-H asymmetric stretching and bending bands at 2870 cm -1 and 1454 cm -1 respectively appear already in SiO 2 /PEG6 spectrum (curve b) whereas the C-C signal (948 cm -1 ) becomes visible as a shoulder only in SiO 2 /PEG24 (curve d).…”

Modulation of indomethacin release from ZrO2/PCL hybrid multilayers synthesized via sol–gel dip coating

“…The band at 1529 cm À1 and the weak shoulder at 1280 cm À1 are attributed to CeC vibrations in AcAc. The peak at 1410 cm À1 is due to methyl CeH symmetric bending [33], whereas the bands at 1026 and 931 cm À1 are assigned to the CeCeH bending mixed with stretching CeC vibrations of AcAc [29].…”

“…3 shows the ATR-FTIR spectra of ZrO 2 coating (curve a) compared with that of ZrO 2 /IND coating (curve b) and pure Indomethacin (curve c). In the ZrO 2 coating spectrum (curve a) the typical peaks of AcAc containing zirconia solegel materials [29] are present. The broad intense band in the region 3600e3000 cm À1 is due to eOH vibrations.…”