Centrosymmetric molecular strings in the hydrogen-bonded structure of 4,4'-bipyridyl–4,4'-thiodiphenol (3/2)

Adducts of meso and racemic 5,5,7,12,12,14-hexamethyl-1,4,8,11-tetraazacyclotetradecane with trigonally trisubstituted benzene carboxylic acids: supramolecular structures in one and two dimensions

“…1), in a motif which may be described as either R 2 2 (10) counting round the C12ÐC13Ð C14 bridge of the macrocycle, or R 3 3 (8) counting across one of the intramolecular NÐHÁ Á ÁN hydrogen bonds. This motif of paired NÐHÁ Á ÁO hydrogen bonds between [(tet-a)H 2 ] 2+ and a carboxylate anion is identical to one found in the hydrated adducts of tet-a with terephthalic acid (Lough et al, 2000), and hence the three-component aggregate in (1) is most simply regarded as containing three R 2 2 (10) motifs. Atom N4 at (x, y, z) acts as a hydrogen-bond donor to O1 within the same asymmetric unit, while N1 at (1 ± x, 1 ± y, 1 ± z) acts as a donor to O2 in the same anion; similarly, N1 at (x, y, z) and N4 at (1 ± x, 1 À y, 1 À z), whose axial N±H bonds project from the research papers…”

“…General comments on the crystal structures. In both (1) and (3) all four of the axial NÐH bonds of the [(teta)H 2 ] 2+ cations are engaged in the formation of NÐHÁ Á ÁO hydrogen bonds: this is also the case in the salt-like adducts formed by tet-a with terephthalic acid (Lough et al, 2000) and with the trigonally substituted 3,5-dihydroxybenzoic acid (VII), itself very closely related to (V) (Gregson et al, 2000). However, in the corresponding adducts formed with bisphenols, or with 3-or 4-hydroxybenzoic acids, only two of the axial NÐH bonds of the [(tet-a)H 2 ] 2+ cation are so engaged, but in the salt formed between the [(tet-a)H 4 ] 4+ cation and the phenylphosphonate anion, [PhP(O) 2 OH] À , all eight NÐH bonds of the cations are involved in intermolecular hydrogen bonding (Gregson et al, 2000).…”

“…The two NÁ Á ÁO distances in the bonds to the carboxylate anion are very different for both (1) and (3), with a difference of well over 0.40 A Ê , while in (4) the corresponding difference is only ca 0.06 A Ê (Table 2). In the tetrahydrated salt formed between teta and terephthalic acid, where the [(tet-a)H 2 ] 2+ cations lie in general positions, the differences between the paired NÁ Á ÁO distances are 0.546 (2) A Ê on one face of the macrocyclic cation and 0.277 (2) A Ê on the other (Lough et al, 2000). Evidently, the interaction of a carboxylate anion with the [C 16 H 38 N 4 ] 2+ cation allows a considerable degree of orientational freedom, consequent upon the sum total of all the inter-ionic interactions, one result of which is the rather wide range of the observed NÁ Á ÁO distances in the NÐHÁ Á ÁO hydrogen bonds.…”

“…The tetra-aza macrocycle 5,5,7,12,12,14-hexamethyl-1,4,8,11tetraazacyclotetradecane, C 16 H 36 N 4 , exists in two isomeric forms: the meso compound [(I), tet-a] and the racemic form [(II), tet-b]. The meso form has been shown to be a versatile building block in supramolecular chemistry (Gregson et al, 2000;Lough et al, 2000), where it generally captures two protons from acidic species to form a dication [C 16 H 38 N 4 ] 2+ in which two H atoms are held in the interior N 4 cavity of the ring, forming a pair of intramolecular NÐHÁ Á ÁN hydrogen bonds. There are four external NÐH bonds roughly normal to the ring and hence this dication could, in principle, act as a fourfold donor in hydrogen-bond formation in which the geometric arrangement of the hydrogen bonds is pre-determined.…”

“…In both cations, it may be expected that there are two NÐH bonds on each face of the macrocycle available for hydrogen-bond formation. It has previously been shown (Lough et al, 2000) that with dicarboxylic acids such as terephthalic acid, the [(tet-a)H 2 ] 2+ cation can form paired NÐ HÁ Á ÁO hydrogen bonds with carboxylate anions, thus giving rise to chain formation.…”