Synthesis, XRD Studies and NLO Properties of [p-H2NC6H4CH2NH3][B5O6(OH)4]·1/2H2O and NLO Properties of Some Related Pentaborate(1−) Salts

The non-metal cation pentaborate(1−) salt [p-H2NC6H4CH2NH3][B5O6(OH)4]·1/2H2O (1) was synthesised from B(OH)3 and p-H2NC6H4CH2NH2 and crystallized from aqueous solution. Compound 1 was characterized by thermal (TGA/DSC), spectroscopic (IR, NMR) and single-crystal X-ray diffraction methods and it was found to crystallize in the non-centrosymmetric point group P21. Powder SHG measurements on 1 and some related alkylammonium pentaborate salts, [NH3CMe2(CH2OH)][B5O6(OH)4], [NH3CMe(CH2OH)2][B5O6(OH)4] and [NH3CHMeCH2OH][B5O6(OH)4], a substituted imidazolium salt, [1,2,3-Me3C3H2N2][B5O6(OH)4], a substituted piperidinium salt, [(CH2)5NH(CH2CH2OH)][B5O6(OH)4], and a substituted pyrrolidinium salt, [S-(+)-2-(HOCH2)C4H7NH2][B5O6(OH)4], were determined. Compound 1 and all compounds, except [1,2,3-Me3C3H2N2][B5O6(OH)4], showed some weak SHG activity with SHG efficiencies of 0.1–0.2 relative to that of KH2PO4 (KDP).