Vibrational spectroscopy and aromaticity investigation of squarate salts: A theoretical and experimental approach

Georgopoulos, Stéfanos Leite; Diniz, Renata; Yoshida, María Irene; Speziali, Nivaldo L.; Santos, Hélio F. Dos; Junqueira, Geórgia M. A.; Oliveira, Luiz Fernando Cappa de

doi:10.1016/j.molstruc.2006.01.035

Cited by 45 publications

(32 citation statements)

References 31 publications

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“…According to calculations, d(NH 2 ) vibration contributes also significantly to this mode. Comparing our theoretical data with experimental IR spectra for HSQand H 2 SQ groups in compounds (I) and (II), respectively, it can be concluded that the IR pattern can be best described as a superposition of the IR maxima of HSQ -and H 2 SQ [38,39]. Compound (III) shows broad and very intense bands at 1492 cm -1 , assignable to a coupled mode of CO and CC stretching, which are calculated at 1487 and 1474 cm -1 with HF and DFT/B3LYP method, respectively.…”

Section: Vibrational Frequencymentioning

confidence: 63%

Three forms of squaric acid with pyrazine and pyridine derivatives: an experimental and theoretical study

et al. 2011

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Section: Vibrational Frequencymentioning

confidence: 63%

Three forms of squaric acid with pyrazine and pyridine derivatives: an experimental and theoretical study

et al. 2011

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“…3.1) is characterized by an underlying complicated IR-spectroscopic pattern like other squaric acid derivatives [7][8][9][10][11][12][13][14]. However in this case the presence of the ammonium cation and H 2 O molecules, both possessing series of stretching and bending characteristic IR-bands, leads to strong overlapping of the bands especially in the 3,500-2,800 cm @1 region.…”

Section: Ir-ld Spectroscopic Datamentioning

confidence: 99%

“…As established in series of systematic crystallographic studies on the self-assembly of squarates and hydrogensquarates [1][2][3][4][5][6]. Detailed studied on the correlation of vibrational spectroscopic properties and structural motifs in squaric acid derivatives have been reported [7][8][9][10][11][12][13][14].…”

Section: Introductionmentioning

confidence: 99%

Crystal structure and spectroscopic properties of ammonium hydrogensquarate squaric acid monohydrate

et al. 2007

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The structure of ammonium hydrogensquarate squaric acid monohydrate has been determined by single crystal X-ray diffraction. The compound crystallizes in the monoclinic space group C2/c and exhibits a 3D network with molecules linked by intermolecular interactions with participation of the H 2 Sq, HSq @ , NH 4 + , and H 2 O species. The HSq @ anion and the neutral H 2 Sq form a strong headto-tail dimer through O-HÁÁÁO hydrogen bonding with lengths of 2.587 and 2.494 Å (protected space between numeral and unit). The layers are connected by ammonium cations and water molecules in a plane through the OÁÁÁN (2.950, 2.978, 3.036 Å ) and OÁÁÁO (2.953, 2.781 Å ) bonds. Another such layer is connected to the NH 4 + cation in the adjacent plane through bifurcated N-HÁÁÁO hydrogenbonding to form a double layer (NHÁÁÁO bond lengths are 3. 036, 2.978, 2.857, 2.909, 2.958, and 2.742 Å , respectively). The IR-band assignment of the compound was achieved using the polarized IR-spectroscopy of oriented colloids in a nematic host. Theoretical ab initio calculations were performed and achieved with a view to explain the IR-bands of the H 2 Sq.HSq @ motif.

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“…31 Since the first synthesis of squaric acid, many kinds of metal squarate salts have been studied with consideration of their crystallographic properties and applications in analytical chemistry. 32,33 In order to get the precise information about π -stacking, investigations on hydrogen free squarate salts are necessary. 34,35 A well-documented example of such π -stabilized metal squarate complexes is sodium squarate (Na 2 C 4 O 4 , SS).…”

Section: Introductionmentioning

confidence: 99%

Compression studies of face-to-face π-stacking interaction in sodium squarate salts: Na2C4O4 and Na2C4O4•3H2O

Wang

et al. 2012

The Journal of Chemical Physics

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High-pressure Raman scattering and synchrotron X-ray diffraction measurements of sodium squarate (Na(2)C(4)O(4), SS) are performed in a diamond anvil cell. SS possesses a rare, but typical structure, which can show the effect of face-to-face π-stacking without interference of other interactions. At ~11 GPa, it undergoes a phase transition, identified as a symmetry transformation from P2(1)/c to P2(1). From high-pressure Raman patterns and the calculated model of SS, it can be proved that the phase transition results from the distorted squarate rings. We infer it is the enhancement of π-stacking that dominates the distortion. For comparison, high-pressure Raman spectra of sodium squarate trihydrate (Na(2)C(4)O(4)●3H(2)O, SST) are also investigated. The structure of SST is determined by both face-to-face π-stacking and hydrogen bonding. SST can be regarded as a deformation of SS. A phase transition, with the similar mechanism as SS, is observed at ~10.3 GPa. Our results can be well supported by the previous high-pressure studies of ammonium squarate ((NH(4))(2)C(4)O(4), AS), and vice versa. High-pressure behaviors of the noncovalent interactions in SS, SST, and AS are compared to show the impacts of hydrogen bonding and the role of electrostatic interaction in releasing process.

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Vibrational spectroscopy and aromaticity investigation of squarate salts: A theoretical and experimental approach

Cited by 45 publications

References 31 publications

Three forms of squaric acid with pyrazine and pyridine derivatives: an experimental and theoretical study

Three forms of squaric acid with pyrazine and pyridine derivatives: an experimental and theoretical study

Crystal structure and spectroscopic properties of ammonium hydrogensquarate squaric acid monohydrate

Compression studies of face-to-face π-stacking interaction in sodium squarate salts: Na2C4O4 and Na2C4O4•3H2O

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