Structure of 1-methyl-1H-imidazole-5-ethanamine dihydrochloride

4-(2-Ammonioethyl)1-methyl-3H+-imida zolium chloride, C6HI3N32+.2C1 , M r = 198"10, monoclinic, P2~/n, a=4-60(1 ) , b = 13-57(1), c = 15.43 (2) A, fl = 98-37 (3) °, V = 952-9 A 3, Z = 4, Dx = 1.381, Om = 1"38 Mg m 3 , F ( 0 0 0 ) = 416, T = 293 K, Mo Ka (A = 0.71069 •), /x = 6.29 mm-1, R = 0.030 for 1484 reflections used in the refinement. Diprotonated methylhistamine molecules are hydrogen bonded through chloride ions. The ethylamine chain is in a trans conformation and the plane defined by three non-H atoms of the chain is perpendicular to the plane of the imidazole ring. Introduction. Ganellin's works on conformation and activity of histamine and methylhistamines have shown that the trans conformation of the ethylamine chain dominates in aqueous solution for all protonated forms and that N-methylation has little influence on the chain conformation (Ganellin, 1973; Ganellin, Pepper, Port & Richards, 1973; Ganellin, Port & Richards, 1973). However, pros-methylation seems to be important for the orientation of the ethylamine chain. Thus we undertook this study as a continuation of the program on structures of histamines and their complexes (Gtbwka, Gatdecki, Kazimierczak & Ma~lifiski, 1980; Gt6wka & Gilli, 1989). Experimental. The crystals of the compound were recrystallized from 2-propanol. D m by flotation. The intensity data to 0max = 25 ° were obtained from a crystal of size 0-44 x 0.38 x 0.15 mm by to/20 scan technique on a CAD-4 diffractometer. Cell constants from setting angles of 25 reflections with 9 < 0 < 15 °. 3 standard reflections, measured every 100 reflections; 2% variation. 5 _< h ___ 5; 0 ___ k <_15; 0 ___ l_< 18. From the 1860 reflections measured, 1637 had I > 30-(/). Absorption was neglected. The structure was solved by direct methods with SHELXS86 (Sheldrick, 1986) and H-atom positions were found from difference Fourier maps. The final agreement factors of 0.030 (R) and 0.041 (wR) were obtained after full-matrix least-squares refinement on F based on 1484 intensities with Fo > 3tr(Fo) (non-H atoms with anisotropic and H atoms with isotropic thermal parameters). The final weighting scheme used was w = k/[tr2(Fo)+ dFo:], where k and d were 0.382 and 0.0079, respectively. (A/o')max -0"08. Max. and min. 0108-2701/90/061025-03503.00 © 1990 International Union of Crystallography 1026 C6H13 N 2 + .2C1heights in final difference synthesis 0-11, -0 .16 e A-3. The calculations were performed on a 1512 Amstrad PC microcomputer with SHELX76 (Sheldrick, 1976). Atomic scattering factors were those in SHELX76. The same crystal structure solved earlier (Gi6wka, C1(1) 1982) has shown disordered position of C1(2) atom. o(2) The population parameters for both positions of the N0) C1(2) atom refined independently during isotropic N(3) N(7) refinement procedure had the values of 0.45 for C(l) CI(2A) and 0.55 for CI(2B). The partially occupied c(2) sites were separated by only 0.223 (1) A. C(4) c(5) C(6) C(7) Discussion. Final atomic parameters and standard deviations are given in Table 1,* while the calculated distances and angles for non-H atoms are collected in Table 2. Fig. 1 shows the overall conformation of the pros-methylhistamine dication and the numbering system used in this study. The crystal structure of the title compound comprises prosmethylhistamine dications hydrogen bonded through chloride anions (Table 2). The molecular geometry of the pros-methylhistamine ion in this structure is very similar to that predicted by Ganellin, Pepper, Port & Richards (1973) for the histamine dication by quantum mechanics and to that found in the histamine diphosphate monohydrate (Veidis, Palenik, Schaffrin & Trotter, 1969). The angles 0~ and 02, where 01 [C(4)--C(5)--C(6)--C(7)] and 02 [C(5)--C(6)--C(7)---N(7)] (Ganellin, Pepper, Port & Richards, 1973), are 94.2 (2) and 174.3 (1) °, respectively, close to 90 and 180 ° for the ideal trans conformation of the ethylamine chain. This and other X-ray studies on diprotonated histamine compounds suggest that the packing is the main factor affecting the ethylamine chain conformation in the crystalline state, as the angle between the imidazole ring and the plane defined by the three non-H atoms of the side chain varies from 4.4 ° in histamine sulfate CYamane, Ashida & Kakudo, 1973), through 7.0 ° in the tetrachlorocobaltate (Bonnet & Jeannin, 1972), 30 ° in the dibromide (Decou, 1964), 78.1 ° in the telemethylhistamine dihydrochloride complex with copper chloride (Gt6wka & Gilli, 1989), and 82.5 ° in histamine diphosphate monohydrate (Veidis, Palenik, Schaffrin & Trotter, 1969) to 96.5 ° in this study. Each chloride ion takes part in two hydrogen bonds with C1...H(N) distances between 2-2 and 2-4 A, and with H..-C1...H angles between 89 and 100 ° . * Lists of structure factors, anisotropic thermal parameters and H-a tom parameters have been deposited with the British Library Documen t Supply Centre as Supplementary Publication No. SUP 52588 (13 pp.). Copies may be obtained through The Technical Editor, Internat ional Union o f Crystal lography, 5 Abbey Square, Chester CH1 2HU, England. Table 1. Atomic positional parameters ( x 105 for CI and x 104 for other non-H atoms) and equivalent isotropic thermal parameters B,,~ = ( 8 7r2 / 3 ) ~.i~jUif12i* aj*ai.aj. x y z 8~ (h 2) 17301 (9) 41329 (3) 9872 (3) 2-84 (1) 37694 (10) 33190 (3) 45107 (3) 3.25 (2) 6289 (3) 446 (I) 1803 (1) 2-55 (3) 3762 (4) 1584 (1) 1083 (1) 3.34 (~) 10828 (4) 1248 (I) 4541 (1) 2.61 (4) 7276 (6) -546 (1) 2090 (2) 3-57 (6) 4117 (4) 625 (2) 1151 (l) 3.03 (4) 5755 (4) 2041 (1) 1693 (1) 3.20 (5) 7381 (4) 1336 (1) 2157 (1) 2.41 (4) 9725 (4) 1406 (1) 2922 (1) 2.56 (5) 8478 (4) 1279 (1) 3775 (1) 2.47 (4) Table 2. Bond lengths (A) and angles (0) and hydrogen-bond geometry N(I)---C(I) 1.468 (2) C(I)--N(I)---C(2) 124.0 (1) N(I)---C(2) 1-333 (2) C(I)---N(1)--C(5) 126-9 (2) N(I)---C(5) 1-389 (2) C(2)--N(1)---C(5) 109.1 (1) N(3)--C(2) 1.314 (2) C(2)--N(3)---C(4) 109-4 (2) N(3)--C(4) 1-364 (2) N(I)--C(2)--N(3) 108-2 (1) N(7)--C(7) 1-482 (2) N(3)--C(4)--C(5) 107-9 (1) C(4)---C(5) 1.353 (2) N(1)--C(5)--C(4) 105-4 (1) C(5)--C(6) 1.481 (2) N(I)--C(5)--C(6) 123-3 (1) C(6)--C(7) 1.520 (2) C(4)--C(5)--42(6) 131.2 (1) C(5)--C(6)--C(7) 111. I (2) C(6)---C(7)--N(7) I11.7 (2) N--H---C1 N---CI N H H---CI N--H---CI N(7)--H(1)...CI(1) i 3.166 (2) 0.90 (3) 2-32 (3) 158 (1) N(7)--H(2)...CI(2)" 3.122 (2) 0-80 (2) 2-34 (2) 169 (1) N(7)--H(3)...CI(1) iii 3.229 (2) 0.91 (3) 2.41 (3) 150 (1) N(3)--H...CI(2) iv 3.091 (2) 0-82 (3) 2-35 (3) 150 (1) Symmetry codes: (i) 0.5 + x, 0.5 y, 0.5 + z; (ii) 1 + x, y, z; (iii) 1.5 x, y 0.5, 0.5 z; (iv) x 0.5, 0.5 y, z 0.5.