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Vibrational analysis ofp-tert-butyl-calix[4]arene conformers byab initiocalculations

“…Partial cone 1,3-alternate 1,2-alternate IR spectroscopy is used generally for characterization of host-guest interactions [11][12][13] in calixarenes [14]. For a reliable explanation of IR spectra an analysis of normal vibrations must be platformed.…”

“…For a reliable explanation of IR spectra an analysis of normal vibrations must be platformed. However, the full interpretation of IR spectra, based on a normal coordinate analysis, has been reported only for the calix [4]arene [13,15]. This research study deals with the interpretation of the vibrational spectra of p-tert-butyl-calix [4]arene, to provide the properties of this compound.…”

Intramolecular co-operative hydrogen bond in calix[n]arenes (n = 4, 6, 8) bearing bulky substituents

“…The band contour is virtually symmetrical, the observed low frequency narrow bands were assigned to the ν(СН) stretching vibrations of the macrocycle fragments, the stretching vibrations of the СН groups in aromatic rings having the highest frequencies among them. [17][18][19] Calixarene 6 is of particular interest, since, apart from the ОН groups at the lower rim of the molecule, it has six СООН groups at the upper one. In the IR spectrum of this derivative, the absorption bands in the region 3540 cm -1 , which are responsible for the non bonding hydroxy fragments of the carboxy groups, are absent.…”

Thiacalix[4]arene’s Lower Rim Derivatives: Synthesis and Supramolecular Properties

“…But they are significantly weaker than in case of conventional calix [4]arene (26-28 kcal•mol -1 for the classic calixarenes and 20-21 kcal•mol -1 for the thiacalixarenes) [15][16][17] because of the ring size of thiacalix [4]arene is 15 % larger than that of calix [4]arene due to the longer bond length of C-S as compared to C-C. For this reason thiacalix [4]arene scaffold is more flexible and easily undergoes conformational changes during the complexation or derivatization. Due to high molecular structure flexibility and a metal-binding ability (the presence of sulfur bridges) thiacalixarenes are superior to conventional calixarenes for the design of supramolecular architectures.…”

“…Unlike to classical calix [4]arenes a synthesis of partially substituted thiacalixarenes is a rather sophisticated problem. The different behavior of these macrocycles is due to energy changes of intramolecular circular hydrogen bonds: 26-28 and 20-21 kcal•mol -1 for calix [4]arenes and thiacalix [4]arenes, respectively, [16,17] and acid-base properties of phenolic groups. [61] In fact, distal disubstituted derivatives can be selectively synthesized using the appropriate reaction conditions for a given substituent.…”