The crystal structure of [Mn(HIDA) 2 (H 2 O) 2 ] (Tetragonal, P42 1 c (no.114), a ϭ b ϭ 8.10(2) Å , c ϭ 9.605(3) Å , α ϭ β ϭ γ ϭ 90°, Z ϭ 2,R ϭ 0.051, wR 2 ϭ 0.123 for 460 observed reflections) consists of infinite acentric 2D square grids with HIDA Ϫ ions as bridging ligands. The 2D grids are interlocked(along the c axis) by hydrogen bonding. The Mn atoms are octahedrally coordinated by four O atoms of four HIDA Ϫ ions (d(MnϪO)ϭ 2.183(4) Å ) and two O atoms of two water molecules (d(MnϪOW) ϭ 2.154(5) Å ).In recent years, low dimensional coordination polymers, generally including one-dimensional (1D) chainlike and two-dimensional (2D) layerlike structures, have received much attention owing to their interesting structural features and potential applications as new solid-state materials, which are different from those of threedimensional(3D) coordination polymers [1Ϫ8]. One of the attractive challenges in this field is the construction of chiral or acentric coordination frameworks as such systems may be exploited for applications in second-order nonlinear optical (NLO) effects (secondharmonic generation, SHG), etc [9Ϫ18]. The iminodiacetic acid (H 2 IDA ϭ [NH(CH 2 COOH) 2 ]) is a multidentate, bridging ligand and can strongly complex metal ions. Some transition metal complexes containing this ligand have been structurally characterized [19Ϫ21]. Recently, the structures and properties of a few transition metal IDA coordination polymers have been reported. Román-Alpiste et al. studied the structures and the magnetic-properties of [Cu(IDA)(H 2 O) 2 ] n constructed from IDA-bridging chains via interchain hydrogen bonds [22]. [Co(IDA)(H 2 O) 2 ] n is 1D chain of Co 2ϩ ions which are bridged by carboxylato groups [23]. [Pb(IDA)] exhibits 3D structure with micro-channels and crystallizing in the acentric space group Fdd2 [24]. Anan'eva et al. determined the crystal structure of [Mn(HIDA) 2 (H 2 O) 2 ] [20], but they did not report its features of the networks and packing. Here, we present 2D square grid structural features of [Mn(HIDA) 2 (H 2 O) 2 ]. Furthermore, we also find that this coordination polymer has a strong second-order nonlinear optical effect, therefore, it has the potential application for optical material.
Results and DiscussionThe crystal structure of [Mn(HIDA) 2 (H 2 O) 2 ] consists of infinite 2D square grids. The asymmetric unit contains 1/4 Mn 2ϩ ion, 1/2 HIDA Ϫ ion and 1/2 water molecule. As shown in Figure 1, the MnThe results show that this acentric coordination polymer exhibits strong powder second harmonic generation (SHG) efficiency, ca. 1.9 times that of potassium dihydrogen phosphate, and remarkable thermal stability.