Halogen NQR and Crystal Structure of Ammonium Halides

The 1 2 7 I-NQR of(HOCH 2 )3 CNH 3 I was determined in the range 77 < T/K<310. At T = 310 K the NQR signal fades out (Tm = 463 K). The 127I spectrum ( T =77 K.): v, =29.195 MHz, v2 = 14.597 MHz, rj(121l)=0, e Q # zz6 _ 1 (1 2 7 I) = 97.315 MHz, is in agreement with the crystal structure. The 127I NQR spectrum of l,3-diammonium-2,2-dimethylpropane diiodide, (H 3 NCH 2 C(CH 3 ) 2 CH 2 N H 3)2+ -2 1 “, is a quartet within the whole temperature range investigated, and the lines correspond to two crystallographically independent iodines: Space group P2x/c, Z = 4, a = 731.2(3) pm, 6 = 689.0(3) pm, c = 2255.1(8) pm, 0 = 104.90(1)°. At 7 = 7 7 K the 127I NQR quartet is (MHz): vx = 34.145, v2 = 32.805, v3 = 22.113, v4 = 16.787; at 295 K (same order, MHz): 30.559, 29.729, 19.810, 15.651. There are two combinations of the NQR frequencies. Considering the coordination of I", the hydrogen bonds N -H • • • I, eQ<PzzQ h ~ \ and tj, we choose for I(1) Vj and v3, for I(2) v2 and v4. At 77 K eQ<Pzzh ~ 1 (I(1))= 118.86 MHz, f?(1 2 7 I(1)) = 0.498, eQ<Pzzh~ l (I(2,) = 109.75 MHz, ^(1 2 7 I(2)) = 0.135 follow for the two iodine atoms. Both, eQ<Pzzh~ 1 (I(1)) and e 0 . , Q h ~ 1 (I<2)) de­ crease smoothly with increasing T\r\(I(2)) increases with increasing T whereas ^(1 2 7 I(1)) is almost constant within 77< T /K < 406. The 7 9 81Br NQR spectrum of l,3-diamino-2,2-dimethylpropane dihydrobromide is also a quar­ tet, showing two crystallographic inequivalent Br atoms in the unit cell. The frequencies are (T =273 K, MHz): vt (7 9 Br)= 14.303, v2 (7 9 Br)= 12.884, (8 1 Br)= 11.951, v2 ( 8 1 Br) = 10.781; space group C2/c, Z = 8 , a = 2136.4(6) pm, 6 = 854.6(3) pm, c = 1125.8(3) pm, /? = 93.23(1)°. Crystal structures and NQR results are discussed.