Polymorphism and optical, magnetic and thermal properties of the either phyllo- or inosilicate-analogous borosulfate Cu[B(SO)].

Two polymorphs of the borosulfate Cu[B(SO)] can be selectively prepared by solvothermal syntheses. The crystal structures of inosilicate-analogous α-Cu[B(SO)] (1̄, no. 2, = 5.2636(2), = 7.1449(2), = 7.9352(2) Å, = 73.698(2)°, = 70.737(2)°, = 86.677(2)°, 65 parameters, = 0.0052) and the new phyllosilicate-analogous polymorph β-Cu[B(SO)] (2/, no. 14, = 7.712(3), = 8.149(3), = 9.092(3) Å, = 111.22(1)°, 3829 independent reflections, 106 parameters, = 0.054) are discussed. Further, the optical, magnetic and thermal properties of both polymorphs are investigated with focus on the role of the Cu cation and its Jahn-Teller effect. The findings are confirmed by DFT calculations yielding insights in the stability of the synthesised polymorphs as well as a predicted γ-modification. Additionally, the crystal structures of two polymorphs of copper hydrogensulfate Cu(HSO)-I (2/, no. 14, = 4.7530(2), = 8.5325(4), = 7.3719(3) Å, = 100.063(1)°, 1063 independent reflections, 55 parameters, = 0.052) and Cu(HSO)-II (1̄, no. 2, = 4.79.88(8), = 7.857(1), = 8.057(1) Å, = 77.86(1)°, = 87.02(1)°, = 89.82(1)°, 1044 independent reflections, 109 parameters, = 0.132) as well as that of Cu[SO] (2/, no. 15, = 6.6341(4), = 8.7302(5), = 9.0555(8) Å, = 104.763(3)°, 1117 independent reflections, 48 parameters, = 0.049) are presented and the cyclosilicate-analogous borosulfate Cu[B(SO)(HSO)] is fully characterised with respect to its optical and thermal properties.