Trimethyl-, triethyl- and trimethoxybenzene-based tripodal compounds bearing pyrazole groups: conformations and halogen-/hydrogen-bond patterns in the crystalline state

Abstract

X-ray analyses of a series of benzene-based tripodal molecules1–9provide interesting insights into the molecular recognition phenomena and give information about the different conformations which adopt the molecules in the solvent-free crystals and in solvates.

Crystalline Ammonium Complexes of Trimethyl‐ and Triethylbenzene‐Based Tripodal Compounds Bearing Pyrazole and Indazole Groups

“…Moreover, the close distance of 3.134(2) Å between Br(2) and N(6) of adjacent molecules and the well defined bond geometry [∠C–Br ··· N 172.9(3)°] indicate the presence of a relatively strong Br ··· N interaction ( n ‐type halogen bond,, , Figure a, Figure b). The pattern of directed noncovalent bonding between the complex molecules is completed by a C–Br ··· π contact (π‐type halogen bond,, Figure c) with a Br ··· C pyrazole distance of 3.368(3) Å which is less than the sum of van der Waals radii of the respective atoms (3.55 Å).…”

“…In the structure of 5 , the dihedral angels between indazole rings are 23.8(1), 51.2(1) and 32.1(1)°, whereas for 6 they are 15.7(1), 55.9(1) and 62.2(1)°. By taking the ethyl groups into account, the conformation of 5 and 6 can be defined as ab′ab′ba′ ; the position of the ethyl groups is marked as a′ and b′ ( b′b′a′ arrangement of the ethyl groups, a′ = Et above and b ′ = Et below; see also refs , …”

“…Furthermore, pyrazole groups have been used for the construction of receptors for neutral molecules, such as mono‐ and disaccharides . It should also be noted that X‐ray analyses of a series of pyrazole‐bearing tripodal compounds with a trimethyl‐, trimethoxy‐ or triethylbenzene scaffold as well as compounds with a hexapodal architecture (hexa‐hosts, ) provided interesting information about the different conformations which adopt the tripodal and hexapodal molecules in the solvent‐free crystals and in solvates. These conformations include beside the most commonly observed ababab conformation also unusual conformations such as aaabbb, aaabab or aaaaaa ( a = above, b = below; position of the side arms above and below the central benzene ring).…”

Crystal structures of monohydrate and methanol solvate compounds of {1-[(3,5-bis{[(4,6-dimethylpyridin-2-yl)amino]methyl}-2,4,6-triethylbenzyl)amino]cyclopentyl}methanol

“…The molecular structures depicted in Figs. 1 and 2 reveal similar host geometries with a fully alternating arrangement of the substituents above and below the plane of the central arene ring [ab'ab'ab' pattern, a = above, b = below (a 0 /b 0 = Et above/below); for a discussion on the conformations of triethylbenzene-based compounds, see: Koch et al, 2017;Schulze et al, 2017]. In other words, the three functionalized side arms point to one face of the central benzene ring and participate in the formation of hydrogen bonds with the guest solvent molecule, while the ethyl groups are directed to the opposite side.…”

Crystal structures of the dioxane hemisolvates ofN-(7-bromomethyl-1,8-naphthyridin-2-yl)acetamide and bis[N-(7-dibromomethyl-1,8-naphthyridin-2-yl)acetamide]

“…Atom Br1 is involved in the formation of a weak C-HÁ Á ÁBr contact. Moreover, the Br1Á Á ÁCg(B) distance of 3.317 (2) Å and the well-defined bonding geometry [C9-Br1Á Á ÁCg(B) = 173.0 (1) ] indicate the presence of an intermolecular BrÁ Á Á halogen bond (Mazik et al, 2010a,b;Koch et al, 2017;Legon, 1999;Megrangolo & Resnati, 2008). The distance of 3.213 (2) Å between atom Br2 and amide atom O1A of an adjacent molecule [symmetry code: (A) x + 1, y À 1, z], which is considerably less than the sum of the van der Waals radii of the respective atoms (3.37 Å ), suggests the existence of an attractive BrÁ Á ÁO halogen bond (Politzer et al, 2007;Koch et al, 2014Koch et al, , 2015.…”