The crystal structure, vibrational spectra, and thermal behavior of piperazinium(2+) selenate monohydrate and N,N '-dimethylpiperazinium(2+) selenatedihydrate

The crystal structure of piperazinium(2+) selenate monohydrate has been res olved; this substance crystallizes in the monoclinic space group P2(1)/n, a = 6.4586(8), b = 11.8335(7), c = 11.8065(7) Angstrom, beta = 100.990(8)deg rees; V = 885.80(13) Angstrom(5), Z = 4, R = 0.0446 for 1556 observed refle ctions. A similar compound, N,N'-dimethylpiperazinium(2+) selenate dihydrat e, crystallizes in a triclinic system with space group P1 and lattice param eters a = 6.7370(8), b = 7.9845(9), c = 12.3802(12) Angstrom, alpha = 92.43 5(9)degrees, beta = 100.219(9)degrees, gamma = 114.699(10)degrees; V = 590. 34(11) Angstrom(3), Z = 2, R = 0.0311 for 2071 observed reflections. While, in the former structure, the cations of piperazinium(2+) in the chair conf ormation are arranged roughly plane-parallel above one another, in the seco nd substance, the N,N'-dimethylpiperazinium (2+) ions lie approximately per pendicularly above one another. The FTIR and FT Raman spectra of both test substances have been measured and studied. The thermoanalytical properties were studied using TG, DTG, and DTA methods in the temperature range 293-53 3 K. DSC measurements were carried out in the temperature range 95-343 K. N o phase transition was found in this temperature region for either of the c ompounds. (C) 2000 Academic Press.