Series of SHG Materials Based on Lanthanide Borate–Acetate Mixed Anion Compounds

Abstract

The first examples of lanthanide borate-acetate mixed anion compounds, namely, Ln2(CH3CO2)2[B5O9(OH)]·H2O (Ln = La 1; Ce 2; Pr 3), were synthesized under hydrothermal conditions. These compounds are isostructural and crystallize in polar space group Cc. They display a unique three-dimensional (3D) framework built by a 3D network of lanthanide borate further decorated by acetate anions. The borate anion exhibits a 2D layer in the ac plane with large 9-member rings (MRs) which are filled by lanthanide(III) ions into a {Ln[B5O9(OH)]}(-) 2D layer. Adjacent {Ln[B5O9(OH)]}(-) layers are bridged by remaining lanthanide (III) ions to form a 3D network of lanthanide borate. It is noteworthy that Ln2(CH3CO2)2[B5O9(OH)]·H2O (Ln = La 1; Ce 2; Pr 3) can be changed into Ln2(CH3CO2)2[B5O9(OH)] (Ln = La 4; Ce 5; Pr 6) under heating at 500 K. Compounds 1-4 display moderate SHG signals of about 2.0, 1.0, 1.4, and 2.5 times that of KH2PO4, respectively, and they are phase matchable. Their SHG responses mainly arise from the synergistic polarization effects of both asymmetric borate clusters and π-conjugated CH3COO(-) anions.

Comparative Interrelationship of the Structural, Nonlinear-Optical and Other Acentric Properties for Oxide, Borate and Carbonate Crystals

“…Crystals 2017, 7, 109 19 of 28 crystals may be "acentric". But, the oxide bond length L(E-O) must be in the interval 124 < (L(E-O < 202 pm in ellipses I and II.…”

“…For the last years, more intensive studies have been carried out in the search and synthesis of new carbon-containing oxide crystals, which are also of higher transparence in the UV spectral ranges [20][21][22][23][24][25][131][132][133][134][135][136][137][138][139][140][141][142][143][144][145] (carbonates [132,138,140,143,144], tartrates [133][134][135]145], formates [136], oxalates [137], acetates [109], and fluoride-carbonates [20][21][22][23][24][25]). These crystals also have their high optical damage threshold and the phase-matching angles in the UV spectral range.…”

“…These crystals also have their high optical damage threshold and the phase-matching angles in the UV spectral range. Besides, many complex carbon-oxide compounds with borates, hydroxides [139,140], having both π-and σ-oxide bonds, and also hydrogen O-H bonds, including borate-carbonate, borate-acetate, borate-formate, borate-oxalate, borate-tartrate and other compounds with several different cations, or anions [109,133,137,[139][140][141][142], are known. The search of such materials was carried out among fluorides, borates, carbonates and their derivatives.…”

Lanthanide Inorganic Solids Based on Main Group Borates and Oxyanions of Lone Pair Cations

“…A number of new compounds with novel architectural features and interesting properties were achieved in lanthanide galloborates, borogermanates, boroantimonates and borotellurates. [5][6][7][8][9][10][11][12][13][14][15] …”

“…[5,6] Ln 2 Ga[B 13 O 21 (OH) 4 ](CH 3 CO 2 ) 2 (Ln＝Y, Sm, Eu, Gd, Dy), as the first examples of mixed-anion lanthanide galloborates, have been obtained through hydrothermal synthesis. [7] These compounds are isomorphic and belong to monoclinic space group C2/c. The structure exhibits a three-dimensional (3D) borate framework, which is composed of [B 7 14-membered-ring (14-MR) channels displaying along the b axis ( Figure 1).…”