X-ray, FTIR,¹H and¹³C NMR, PM3 and AM1 studies of (N—H⋯N)⁺and (O—H⋯O)^–hydrogen bonds in a complex of 1,8-diaminonaphthalene with maleic acid: proton cavity and basicity of proton sponges

Abstract

The crystal structure of the title complex h a s been determined by X-ray analysis. All H atoms were located and refined isotropically ; R = 0.041 for 1595 observed reflections. The intramolecula: hydrogen bonds are asymmetrical and are characterized by the following distances and angles: 2.670 (3) . A and 146 (3)" for t h e (NHN)+ bridge in t h e protonated 1,8-diaminonaphthalene cation (DAN+H) and 2.423 (2) A and 177 (3)" for the (OH0)bridge in t h e hydrogen maleate anion (HM-). The NaH, group is engaged in two intermolecular bonds with the anion [N+(H)..-O distances 2.794 (2) and 2.856 (3) 6\]. The interactions of t h e NH, group with the anion are weaker [N(H). --0 distances 3.078 (3) and 3.225 (3) A]. Most of the bond distances and angles in DAN'H -HMare very similar to those in the complex of 1,8-bis(dimethylamino)naphthalene with maleic acid, DMAN+H 1) HM-. The deformations of the naphthalene skeleton in DAN+H.HM-and DMAN+H.HM-are also comparable. In DMAN+H, the proton is located in a cavity formed by four methyl groups, therefore, its exchange is slow on the NMR timescale. In DAN+H t h e proton is not inside a cavity and the exchange becomes rapid. Although spherical repulsions are not negligible, t h e cavity is of prime importance for t h e large basicity of DMAN. The PM3 method reproduces correctly the cation structure and its interactions with t h e anion but t h e 0. + .O distance in the anion is too long. The AM1 method failed to reproduce t h e structure of the complex correctly.'Proton sponges' are commonly associated with 1,8-bis(dimethylamino)naphthalene, DMAN, and its derivatives. The extraordinarily high basicity'-, of these compounds has led to a continuous interest in their proper tie^.'.^-'^.Recently we have studied the H-bonds in the complex of 1 ,8-bis(dimethylamino)naph thalene with maleic acid, DMAN'H-HM-, and found that the geometries of the N-H...N and O-H*.-O bridges of the cation and anion are dominated by spherical repulsions of their constituent atoms.', In this paper we extend our investigations to include a complex of the parent compound, 1,sdiaminonaphthalene-maleic acid, DAN" H HM -, to answer the question why only tetraalkyl derivatives of 1,8diaminonaphthalene are more basic than most aliphatic a m i n e ~. ~ DAN is not a proton sponge (pK, = 4.61; cf. pK, = 12.1 for DMAN);' its structure has been determined by X-ray crystallography. I 2 * I 4 Experimental DAN was purified by crystallization from methanol-water. DAN'H'HM-was prepared by mixing maleic acid (0.01 mol) with DAN (0.01 mol) in 2 cm3 acetonitrile. The product was recrystallized from ethanol; mp 140-141 "C.

Hydrogen-bonding one-dimensional chains containing theR42(8) motif in the ammonium salts 1-naphthylammonium iodide and naphthalene-1,8-diyldiammonium diiodide

“…In the latter case, the repulsion is partly countered by an attractive intramolecular hydrogen bond, and the NÁ Á ÁN distances are 2.72 and 2.74 Å for the two molecules in the asymmetric unit. In the monoprotonated salts, the distances are 2.72 Å for both LECCIF and LECCOL (Basaran et al, 1993) and 2.67 Å for YEWRIB (Bartoszak et al, 1995). Compound (II) has no intramolecular hydrogen bond and the N1Á Á ÁN2 distance is thus longer at 2.92 (1) Å .…”

“…In the diaminonaphthalene case, monoprotonated salts are more common. Counter-ions in these structures include dichloroacetate (LECCIF; Basaran et al, 1993), trichloroacetate (LECCOL; Basaran et al, 1993) and maleate (YEWRIB; Bartoszak et al, 1995). No diprotonated 1,8-diaminonaphthalene salts are reported in the CSD.…”

Unusual 2:3:2 complex of DABCO mono-betaine with HCl and H2O studied by X-ray diffraction, DFT calculations and spectroscopic methods

“…The OÁHÁO hydrogen bonds with the OÁÁÁO distances <2.5 Å are present in the following three classes of compounds: (i) acids salts of carboxylic acids (AHA) À M + , where M = Na, K, Rb, Cs, NH 4 [1][2][3][4], (ii) basic salts of heterocyclic N-oxides and other oxygen bases with acids, (BHB) + X À , where X = Cl, Br, I, ClO 4 , BF 4 [5][6][7][8][9][10][11] and (iii) basic salts of zwitterionic molecules with acids, (BHB) + X À . Olovsson et al [35] divided all complexes with very short OÁHÁO hydrogen bonds into four groups: (a) symmetric or centered, with the proton located precisely at the center of the OÁÁÁO distance; (b) statically disordered with the proton closer to one or the other oxygen atom in different domains on the crystal; (c) dynamically disordered, where proton jumps between the two positions in the same hydrogen bonds [a dynamic analogue of (b)]; and (d) asymmetric with the proton closer to one of the oxygen atoms.…”

Reducing the Hygroscopicity of the Anti-Tuberculosis Drug (S,S)-Ethambutol Using Multicomponent Crystal Forms

“…Ethambutol Maleate (ETBMAL, 1:2). This salt crystallizes in the orthorhombic space group P2 34,35 Despite the unit cell differences (Table 1), this salt has some similarities at supramolecular level with the oxalate salt (see Figures 1a and 7) motif (Figure 2c). As observed in the ETOXA structure, these chains run in opposite directions along the [100] and are perpendicularly stacked along the [001] direction (Figure 2a).…”

“…These supramolecular features might explain the differences found for the C−O and CO bond lengths. 34,35 These chains are perpendicularly stacked along the [010] direction, as shown in Figure 1a.…”