Cation binding resorcinarene bis-crowns: the effect of lower rim alkyl chain length on crystal packing and solid lipid nanoparticles

A perspective to resorcinarene crowns

“…Another alternative for more restricted approach for bridging was to choose tetramethoxy resorcinarene 12 as a platform for resorcinarene crowns. 16,17 Tetramethoxy resorcinarene, first synthesized by…”

Influence of lower rim C-methyl group on crystal forms and metal complexation of resorcinarene bis-crown-5

“…28 The longer alkyl chain tetramethoxy resorcinarenes (C 2 H 5 -C 11 H 23 ) have previously been used as starting materials for resorcinarene bis-and mono-crown-5 derivatives, which are synthesized by attaching one or two tetra(ethyleneglycol) bridges to the hydroxyl groups at the upper rim. 29,30 The crown ether bridged resorcinarene derivatives with a fixed boat conformation have shown a reasonable affinity towards ammonium cations, 31 33 and a helical chain, 29 especially for the metal complexes of C-ethyl resorcinarene bis-crown-5, have been observed. The comparison of the C 2 H 5 -C 11 H 23 derivatives of resorcinarene bis-crown-5 has indicated that lower rim alkyl chain affects the self-assembly and crystal packing of the bis-crown-5, but also the complexation properties of the host probably due to solubility differences.…”

“…Form 1-I was also obtained from ethyl acetate and several co-crystallization experiments with silver and alkali metal salts, which indicates the stability of this crystal form. Previously, unsolvated crystal forms have only been obtained for C-butyl and C-pentyl resorcinarene bis-crown derivatives, 30 whereas C-ethyl derivative has crystallized as various solvate structures. The conformation of 1 in polymorph 1-I is a twisted boat with an 8.8° tilt angle between the vertically aligned aryl rings and a 12.3° twist angle with respect to the methine bridges (Fig.…”

“…In addition, the upper rim hydroxyl group is hydrogen bonded to the (4)), which is rotated sideways on top of the cavity. 30,32 Difference to the structures of the longer alkyl chain resorcinarenes lie in the conformation of 1 (Table 3), which is less twisted than C-propyl bis-crown but more twisted than C-ethyl bis-crown. In addition, 1 has a larger dihedral angle of 161.0° between the horizontal aromatic rings than C-ethyl and C-propyl derivatives (152.6° and 148.8°), which leads to a longer Cs···Cs distance (6.90 Å) than in previous complexes (6.42 Å and 6.57 Å for C-ethyl and Cpropyl derivatives, respectively).…”

“…The comparison of the C 2 H 5 -C 11 H 23 derivatives of resorcinarene bis-crown-5 has indicated that lower rim alkyl chain affects the self-assembly and crystal packing of the bis-crown-5, but also the complexation properties of the host probably due to solubility differences. 30,34 These results prompted us to study how the conformational properties of the C-methyl resorcinarene manifest in the resorcinarene crown ether derivatives C-methyl bis-crown-5 and mono-crown-5, which turned out to show remarkably different solvate formation and crystal packing properties than their longer alkyl chain analogues.…”