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Now showing 1 - 10 of 83
  • Publication
    From the Isolated Molecule to the Crystal: A Study of Isomerism, Photochemistry and Polymorphism in Hydantoin Derivatives
    (2017) Nogueira, Bernardo, A.; Canotilho, Joa; Henriques, M. S. C.; Eusebio, M. E. S.; Rui, Fausto; ILDIZ, GÜLCE ÖĞRÜÇ; 107326
  • Publication
    Theoretical DFT, FT-IR and NMR studies of 2-methoxy-6-(5-H/Me/Cl/NO2-1H-benzimidazol-2-yl)-phenols
    (2016) Tavman, Aydın; Boz, İsmail; Çınarlı, Adem; Gürbüz, Demet; ILDIZ, GÜLCE ÖĞRÜÇ; 113687; 9895; 107326; 175977; 126375
  • Publication
    Composition analysis of soybean salt resistant mutants by raman spectroscopy and chemometrics
    (2019) Yılmaz, Ayberk; Kabuk, Hayrunnisa Nur; Kaygısız, Ersin; Fausto, Rui; MERİÇ, SİNAN; AYAN, ALP; ATAK, ÇİMEN; ÇELİK, ÖZGE; ILDIZ, GÜLCE ÖĞRÜÇ; 107326; 6653; 175748; 185510; 219257; 113987
    Soya seeds belonging to fourth generation mutants (M
  • PublicationRestricted
    Conformational Analysis, Spectroscopy and Photochemistry of Matrix-Isolated 1H- and 2H- Tautomeric Forms of Ethyl Tetrazole-5-Carboxylate
    (Elsevier Science, 2021) ILDIZ, GÜLCE ÖĞRÜÇ; Fausto, Rui
    The preferred conformations, infrared spectra and photochemistry of matrix-isolated 1H and 2H tautomers of ethyl tetrazole-5-carboxylate (ET5C) were investigated. Experimentally, isolated monomeric forms of the two tautomers were trapped in cryogenic argon matrices (15 K), and studied by infrared spectroscopy. Identification of the conformational species trapped in the matrices was undertaken by combining the experimental spectro-scopic data with results of quantum chemical calculations performed at the DFT(B3LYP)/6-311++G(d,p) level of theory. For each tautomer, two conformers were observed in the matrices, all forms exhibiting the ester group in the anti configuration (C-O-C-C dihedral equal to 180 degrees). In turn, the conformers having a gauche ester group that are predicted by the calculations to be significantly populated in the gas phase equilibrium (room temperature), were found to convert into the anti forms during matrix deposition (conformational cooling). Very interestingly, and contrarily to what is in general found for tetrazoles, the 1H tautomer is the most stable tautomer of ET5C, and strongly predominates in the studied matrices. Narrowband UV irradiation (lambda = 250 nm) was found to lead to tetrazole fragmentation, with release of molecular nitrogen and production of four isomeric photoproducts (diazirine, cyanamide, carbodiimide and nitrile imine), all of them being successfully identified through comparison of the experimental spectroscopic spectra of the irradiated matrices with the DFT(B3LYP)/6-311++G(d, p) predicted infrared spectra of these species. This study also stresses the structural relevance of the N-H//O = C intramolecular interaction between the ring hydrogen atom and the carbonyl group of the substituent in the 1H tautomer of ET5C.
  • Publication
  • PublicationRestricted
    A New Tetramine Bis(2-Naphthol)-Derivative Fluorescent Chemosensor for Aluminum Ion (Al3+)
    (Elsevier, 2022) Golbedaghi, Reza; ILDIZ, GÜLCE ÖĞRÜÇ; Azadbakht, Reza; Fausto, Rui
    A new tetramine bis(2-naphthol)-derivative was synthesized and its structure investigated by H-1- and C-13 NMR, UV-Vis absorption and fluorescence spectroscopies, as well as through density functional theory calculations (including time-dependent DFT). The effect of a series of metal ions (Ag+, Al3+, Ba2+, Ca2+, Cd2+, Co2+, Cs (+), Cu2+, Fe2+, Fe3+, K+, Mg2+, Mn2+, Ni2+, Pb2+ and Zn2+) on the fluorescence spectra of the synthesized compound was then investigated and it was observed that the presence of Al3+ ion causes a strong increase in the fluorescence emission of the ligand, by about 70 times. This exceptional intensification is specific for Al3+ within the whole series of ions investigated, together with the selectivity found for many of the remaining ions (in particular the ions of Groups I and II of the Periodic Table and Mn2+), makes the compound a promising candidate to act as chemosensor for Al3+. Possible structures for the ligand:Al3+ complex are suggested based on DFT results. TD-DFT calculations performed on these structures suggest that the fluorescence enhancement upon binding of Al3+ to the ligand results most probably from metal-to-ligand charge transfer where the acceptor groups of the ligand are the naphthol moieties. (C) 2021 Elsevier B.V. All rights reserved.
  • Publication
    Theoretical and Experimental Vibrational Analysis of Hydantion
    (2010) ILDIZ, GÜLCE ÖĞRÜÇ; 107326
  • Publication
    Behaviour Of Different Materials Against Sr 90 Beta Source
    (2004) ILDIZ, GÜLCE ÖĞRÜÇ; 107326
  • Publication
    A Multi-Technique Approach to the Study of Hydantoins
    (2017) ILDIZ, GÜLCE ÖĞRÜÇ; 107326
  • PublicationOpen Access
    Structure, Vibrational Spectra, and Cryogenic MatrixPhotochemistry of 6-Bromopyridine-2-Carbaldehyde: From the Single Molecule of the Compound to the Neat Crystalline Material
    (MDPI, 2023) Brito, Anna Luiza B.; Lopes, Susy; ILDIZ, GÜLCE ÖĞRÜÇ; Fausto, Rui
    6-Bromopyridine-2-carbaldehyde (abbreviated as BPCA) is used both as a building block in supramolecular chemistry and as a ligand for transition metal catalysts and luminescent complexes. In this study, the structure and vibrational spectra of BPCA were investigated in both the room temperature neat crystalline phase and for the compound isolated in cryogenic Ar, Kr and Xe matrices. The experimental studies were complemented by quantum chemical DFT(B3LYP)/6-311++G(d,p) calculations. For the crystalline compound, infrared and Raman spectra were obtained and interpreted. Comparison of the obtained infrared spectrum of the crystal with those obtained for the isolated molecules of BPCA in the studied cryomatrices helped to conclude that the intermolecular interactions in the crystal do not significantly perturb the intramolecular vibrational potential. Structural analysis further supports the existence of weak coupling between the intermolecular interactions and the structure of the constituting molecular units in crystalline state. The intermolecular interactions in the BPCA crystal were also evaluated by means of Hirshfeld analysis, which revealed that the most important interactions are weak and of the (HN)-N- horizontal ellipsis , (HO)-O- horizontal ellipsis , (HH)-H- horizontal ellipsis , (HBr)-Br- horizontal ellipsis and (BrBr)-Br- horizontal ellipsis types. The conformer of BPCA present in the crystal was found to correspond to the most stable form of the isolated molecule (trans), which bears stabilizing C-(HO)-O- horizontal ellipsis =C and C(=O)(HN)-N- horizontal ellipsis interactions. This conformer was shown to be the single conformer present in the as-deposited cryogenic matrices prepared from the room temperature gaseous compound. Broadband UV irradiation of matrix-isolated BPCA (lambda >= 235 nm) resulted in the conversion of the trans conformer into the higher-energy cis conformer, where repulsive C-(HH)-H- horizontal ellipsis -C(=O) and C=(OLPLPN)-N- horizontal ellipsis (where LP designates a lone electron pair) interactions are present, and decarbonylation of the compound with formation of 2-bromopyridine (plus CO). The decarbonylation reaction was found to be more efficient in the more polarizable Xe matrix, indicating stabilization of the radicals initially formed upon breaking of the C-C(HO) and C-H (aldehyde) bonds in this medium, and testifying the occurrence of the decarbonylation reaction with involvement of radical species. TD-DFT calculations were used to access the nature of the excited states associated with the observed UV-induced reactions. As a whole, this study provides fundamental data to understand the physicochemical behavior of the compound, bridging the properties of the isolated molecule to those of the neat crystalline com-pound. Such information is of fundamental importance for the understanding of the role of BPCA in supramolecular chemistry and to potentiate its applications in synthesis and as a ligand for transition metal catalysts and luminescent complexes.