title: IR and NMR spectra, intramolecular hydrogen bonding and conformations of para-tert-butyl-aminothiacalix[4]arene in solid state and chloroform solution.
abstract: It is demonstrated that dissolution of aminothiacalix[4]arene in chloroform results in transformation of 1,3-alternate conformation, adopted in single-crystal and bulk polycrystalline solids, to the pinched-cone form. This conformer is stabilised by the intramolecular hydrogen bonds of two distal amino-groups acting as H-donors with another two amino moieties that appear as H-acceptors. The H-bonds cause quite small (ca. 10-20 cm(-1)) red shift of the IR bands of the NH(2) stretching vibrations, which suggests rather weak NHcdots, three dots, centeredN hydrogen bonding. This latter is sufficient to stabilize the pinched-cone conformation in the chloroform solution, but the energy gap between the pinched-cone and other conformations is small, and solid-state intermolecular forces easily overcome it, leading to realisation of the 1,3-alternate conformer. The comparison of the DFT computed and experimental vibrational and NMR spectra demonstrates good quality of present quantum-chemical computations, allows complete interpretation of the spectra and reveals simple IR and NMR spectroscopic markers of the conformers of aminothiacalix[4]arenes.
authors.affiliation: AEArbuzov Institute of Organic and Physical Chemistry, Kazan Scientific Centre of the Russian Academy of Sciences, Arbuzov str 8, 420088 Kazan, Russia.
authors.forename: Elena E
authors.initials: EE
authors.lastname: Zvereva
authors.forename: Sergey A
authors.initials: SA
authors.lastname: Katsyuba
authors.forename: Alexander E
authors.initials: AE
authors.lastname: Vandyukov
authors.forename: Alla V
authors.initials: AV
authors.lastname: Chernova
authors.forename: Valery I
authors.initials: VI
authors.lastname: Kovalenko
authors.forename: Svetlana E
authors.initials: SE
authors.lastname: Solovieva
authors.forename: Igor S
authors.initials: IS
authors.lastname: Antipin
authors.forename: Alexander I
authors.initials: AI
authors.lastname: Konovalov
mesh_terms: D047250:Calixarenes / Q000737:chemistry*; D002725:Chloroform / Q000737:chemistry*; D006860:Hydrogen Bonding; D009682:Magnetic Resonance Spectroscopy; D008956:Models, Chemical; D008958:Models, Molecular; D008968:Molecular Conformation; D015394:Molecular Structure; D011789:Quantum Theory; D012996:Solutions; D013055:Spectrophotometry, Infrared; D017550:Spectroscopy, Fourier Transform Infrared
chemical_list: D012996:Solutions; C549000:para-tert-butyl-aminothiacalix(4)arene; D047250:Calixarenes; D002725:Chloroform