A 2:1 complex of 2,4-dinitroaniline and 1,4,7,10,13,16-hexaoxacyclooctadecane (18-crown-6)

A 1:1 Host-Guest Complex between 1,4,7,10,13,16-Hexaoxacyclooctadecane ('18-crown-6') and m-Nitroaniline: Mere Stoicheiometry or a Genuine 1:1 Adduct ?

“…The overall arrangement of the adducts (see Fig. 2) is similar to those previously found [9,12,13]: Two nitroaniline molecules, related by a centre of inversion, are inclined with dihedral angles 66(1)° (for A) and 53(1)° (for B) 'above' and 'below' the planes formed by the six 0 atoms of the macrocycles (co-planar to within ± 26 pm in both crowns). Four strong and (possibly) two more very weak H bridges (Table V) link guest and host molecules in a pattern resembling that of 18-crown-6/^-nitroaniline 1:2 [11] (Fig.…”

“…2522 (2) 3567 (2) 3746 (1) 73 1)* C (2) 2378 (3) 2019 (3) 3902 (2) 82 1)* C (3) 743 (3) 1686 (3) 3828 (2) 78 1)* 0(4) -300 (2) 2086 (2) 4645 (1) 73 1)* 0 (5) -1902 (4) 1953 (3) 4568 (2) 84 1)* C (6) -2940 (3) 2362 (3) 5454 (2) 87 1)* 0 (7) -3036 (2) 3907 (2) 5390 (1) 78 1)* 0 (8) -4024 (3) 4403 (3) 6205 (2) 90 1)* 0 (9) -3984 (3) 6023 (3) 6104 (2) 89 1)* 0 (10) 2850 (2) 5731 (2) 406 (1) 78 1)* 0 (11) 3409 (3) 4865 (3) 1211 (2) 82 1)* 0 (12) 3398 (3) 3281 (3) 1112 (2) 79 1)* 0 (13) 1819 (2) 2846 (2) 1266 (1) 74 1)* 0 (14) 1679 (3) 1389 (3) 1123 (2) 82 1)* 0 (15) 9 (3) 1084 …”

“…one guest molecule (or one donor group of a bifunctional guest molecule [5]) is attached to each side of the macrocycle. This also holds for the recently reported series of adducts with hydrazines [8,9] and anilines [10][11][12][13]. It was therefore surprising that elemental analysis [10] and cell volume of the title compound (V ca.…”

A 2:1 complex of 4-nitro-1,2-benzenediamine and 1,4,7,10,13,16-hexaoxacyclooctadecane (18-crown-6)

“…In the molecular complexes of 18-crown-6 investigated so far, bifurcated H bridges (as defined by Donohue, 1968) are observed only when more than one electron-withdrawing group renders H atoms sufficiently acidic (Hilgenfeld & Saenger, 1981;Weber & Sheldrick, 1981). This also applies for the present structure, where the 4-nitro-l,2-benzenediamines are linked to the ligand only by 'normal' bonds (see Table 5).…”

“…C (2) The decreased acidity of the NH 2 groups, as compared to 2,4-dinitroaniline (Weber & Sheldrick, 1981), is reflected in C(12)-N(19) and C(13)--N(20) bonds of 1.378 (4) and 1.367 (3) A, respectively, comparable to C-NH 2 distances in non-complexing o-nitroaniline (Dhaneshwar, Tavale & Pant, 1978) and 3-aminopyridine (Chao, Schempp & Rosenstein, 1975) but slightly shorter than in 1,2-diaminobenzene and its hydrochloride (Sfftlhandske, 1976). Accordingly, a systematic distribution of bond lengths in the benzene ring is less distinct; but the lengthened C(12)-C(13) bond of 1.420 (3)/k (between the two amine functions) may give some evidence for a contribution of quinonoid canonical forms to the overall resonance state.…”