Crystal structures of the nitrate salt of 24-pyrimidinium crown 6 {5,12,19,26,33,40-hexaamino-3,10,17,24,31,38-hexamethyl[1.6 ]- (1,5)pyrimidiniophane} and its degradation product in water–methanol mixtures

Abstract

Reflux of thiamin [3-(4-amino-2-methylpyrimidin-5-ylmethyl)-5-(2-hydroxyethyl)-4-methylth iazolium] mononitrate in methanol for 2 h, followed by recrystallization from methanol, produced single crystals of [L][NO ₃ ] ₆ ·16H ₂ O {L = 5,12,19,26,33,40-hexaamino-3,10,17,24,31,38-hexamethyl[1. ₆ ](1,5)pyrimidiniophane, or 24-pyrimidinium crown 6}. The compound crystallizes in the rhombohedral space group R, a = b = c = 14.131(11) Å, α = β = γ = 115.26(5)°, Z = 1, R = 0.0469, 1352 independent reflections with F > 2.0σ(F). Reflux of [L][NO ₃ ] ₆ ·16H ₂ O in methanol–water (3∶2) for 182 h produced single crystals of the nitric acid salt of 4-amino-5-methoxymethyl-2-methylpyrimidine. The compound crystallizes in the triclinic space group P, a = 9.116(6), b = 9.452(5), c = 12.742(8) Å, α = 101.14(5), β = 107.13(5), γ = 93.27(5)°, Z = 4, R = 0.0644, 2690 independent reflections with F > 2.0σ(F). The nitric acid salt of 4-amino-2-methylpyrimidine-5-methanol has been isolated and identified by ¹ H NMR spectroscopy from the thermal decomposition reaction of [L][NO ₃ ] ₆ ·16H ₂ O in water. The alcohol has also been observed by ¹ H NMR spectroscopy in the decomposition of [L] ⁶⁺ in aqueous solutions at room temperature.