Inorganic salts of biguanide – Searching for new materials for second harmonic generation

Five inorganic salts of biguanide with carbonic, nitric, phosphoric and phosphorous acids were prepared and X-ray structural analysis has been performed for three novel compounds. Biguanidium(1+) phosphite trihydrate crystallizes in the triclinic space group P1¯, a = 7.1470(1) Å, b = 9.6530(2) Å, c = 11.3140(2) Å, α = 70.094(1)°, β = 75.688(1)°, γ = 86.099(1)°, V = 713.71(2) Å3, Z = 2, R = 0.0350 for 3031 observed reflections. The crystal structure is based on a network of phosphite anions and water molecules. Biguanidium(1+) cations form pairs through two intermolecular hydrogen bonds of the N–H…N type and fill the network with anions and water molecules.Biguanidium(2+) phosphite monohydrate crystallizes in the triclinic space group P1¯, a = 6.9690(2) Å, b = 7.3500(3) Å, c = 8.1730(3) Å, α = 82.518(2)°, β = 83.015(2)°, γ = 82.811(2)°, V = 409.44(3) Å3, Z = 2, R = 0.0308 for 1779 observed reflections. The structure is formed of a network of alternating biguanidium(2+) cations, phosphite anions and pairs of water molecules interconnected by a system of intermolecular hydrogen bonds.Biguanidium(2+) hydrogen phosphate monohydrate crystallizes in the triclinic space group P1¯, a = 7.0630(2) Å, b = 7.8740(3) Å, c = 8.1120(3) Å, α = 102.706(2)°, β = 104.976(2)°, γ = 92.632(3)°, V = 422.61(3) Å3, Z = 2, R = 0.0337 for 1827 observed reflections. The crystal structure is formed by pairs of anions that are mutually connected in chains through two water molecules. These chains are interconnected by biguanidium(2+) cations to form a three-dimensional network.The FTIR and FT Raman spectra of all five compounds were recorded, calculated (HF, B3LYP and MP2 methods) and discussed.Quantitative measurements of second harmonic generation of powdered biguanidium(2+) nitrate and novel biguanidium(2+) carbonate monohydrate at 800 nm were performed and a relative efficiency (compared to KDP) of 87% and 20% was observed, respectively.