A doubly annelated triple calix[4]arene in the cone/1,2-alternate/cone conformation

The doubly annelated triple calix[4]arene 2a, substituted by four nitro groups was synthesised by fragment condensation of the known exo-calix[4]arene 3 and the bisbromomethylated dimer of p-nitrophenol 4. Single crystals of its calcium salt [({[Ca .(DMSO)(4).(H2O)(2)](2+)(4DMSO)} (2a - 2H)(2-)) 2DM...

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Bibliographic Details
Published inJournal of the Chemical Society, Perkin Transactions 2 no. 12; pp. 2777 - 2782
Main Authors Paulus, EF, Frings, M, Shivanyuk, A, Schmidt, C, Bohmer, Vogt, W
Format Journal Article
LanguageEnglish
Published CAMBRIDGE Royal Soc Chemistry 01.12.1998
Subjects
Chemistry
Chemistry, Organic
Chemistry, Physical
Physical Sciences
Science & Technology
P-TERT-BUTYLCALIX ARENE
DIMETHYLFORMAMIDE
CALIX ARENE
CRYSTAL-STRUCTURES
COORDINATION
DIMETHYL-SULFOXIDE
PARA-TERT-BUTYLCALIX ARENE
LANTHANIDE ION COMPLEXES
METAL-COMPLEXES
CALIXARENES
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Summary:The doubly annelated triple calix[4]arene 2a, substituted by four nitro groups was synthesised by fragment condensation of the known exo-calix[4]arene 3 and the bisbromomethylated dimer of p-nitrophenol 4. Single crystals of its calcium salt [({[Ca .(DMSO)(4).(H2O)(2)](2+)(4DMSO)} (2a - 2H)(2-)) 2DMSO] were obtained from DMSO water containing Ca(HCO3)(2). Their X-ray analysis, the first crystallographic proof of the constitution of an annelated calixarene, shows both monoprotonated cndo-calix[4]arene structures in the expected cone conformation, while the exo-calix[4]arene in the middle of the molecule is fixed in the 1,2-alternate conformation. The Ca2+ ion is completely solvated by four DMSO and two water molecules in a slightly distorted octahedral fashion. Each water binds two further DMSO molecules, one of which is included ire the cavity of the exo-calix[4]arene parts, leading in this way to infinite chains of anions and cations. No direct contact between the Ca2+-ion and the phenolate oxygens or the aromatic pi-electron systems of 2a is present. The pK(a)-values for the first deprotonation step of each endo-calix[4]arene part of 2a are similar to an analogous calix[4]arene 5 with two adjacent p-nitrophenol units, while in contrast to 5 no further deprotonation can be observed.
ISSN:1472-779X
0300-9580
1364-5471
DOI:10.1039/a708088c