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 -H 2 NC 6 H 4 CH 2 NH 3 ][B 5 O 6 (OH) 4 ]·1/2H 2 O ( 1 ) was synthesised from B(OH) 3 and p -H 2 NC 6 H 4 CH 2 NH 2 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 P 2 1 . Powder SHG measurements on 1 and some related alkylammonium pentaborate salts, [NH 3 CMe 2 (CH 2 OH)][B 5 O 6 (OH) 4 ], [NH 3 CMe(CH 2 OH) 2 ][B 5 O 6 (OH) 4 ] and [NH 3 CHMeCH 2 OH][B 5 O 6 (OH) 4 ], a substituted imidazolium salt, [1,2,3-Me 3 C 3 H 2 N 2 ][B 5 O 6 (OH) 4 ], a substituted piperidinium salt, [(CH 2 ) 5 NH(CH 2 CH 2 OH)][B 5 O 6 (OH) 4 ], and a substituted pyrrolidinium salt, [ S -(+)-2-(HOCH 2 )C 4 H 7 NH 2 ][B 5 O 6 (OH) 4 ], were determined. Compound 1 and all compounds, except [1,2,3-Me 3 C 3 H 2 N 2 ][B 5 O 6 (OH) 4 ], showed some weak SHG activity with SHG efficiencies of 0.1–0.2 relative to that of KH 2 PO 4 (KDP).