Organic–inorganic hybrid materials assembled through weak intermolecular interactions. Synthesis, structures and non-linear optical properties of [4,4′-bipyH2][M(NCS)4] (M = Mn2+, Co2+ or Zn2+; 4,4′-bipy = 4,4′-bipyridine)

Abstract

Three compounds [4,4′-bipyH₂][M(NCS)₄] (M = Mn²⁺, Co²⁺ or Zn²⁺; 4,4′-bipy = 4,4′-bipyridine) were obtained from the reactions of 4,4′-bipy with M(SCN)₂ in acidic solution and their crystal structures determined by single-crystal X-ray diffraction. All crystallise isomorphously in the chiral orthorhombic space group P2₁2₁2. The tetrahedral [M(NCS)₄]²⁻ anions are inter-connected by S⋯S contacts (ca. 3.63 Å) and are hydrogen bonded with the diprotonated [4,4′-bipyH₂]²⁺ cations [N⋯S 3.241 Å in 1; 3.235 Å in 2; 3.239 Å in 3] to form two-dimensional, highly wavy networks with hourglass-shaped cavities (ca. 12.3 Å long; 9.4 Å wide at the ends, 6.8 Å at the waist). These two-dimensional networks are stacked with each other to furnish a channel accommodating the diprotonated [4,4′-bipyH₂]²⁺ cations. The three organic–inorganic hybrid compounds are thermally stable with melting points above 230 °C. The powder second harmonic generation efficiencies were measured as moderate.