Two novel acentric borate fluorides: M3B6O11F2 (M = Sr, Ba)

Inorg Chem. 2012 Apr 2;51(7):3953-5. doi: 10.1021/ic202318b. Epub 2012 Mar 12.

Abstract

Two novel, noncentrosymmetric borate fluorides, Sr(3)B(6)O(11)F(2) and Ba(3)B(6)O(11)F(2), have been synthesized hydrothermally and their structures determined. The compounds are isostructural, crystallizing in space group P2(1), having lattice parameters of a = 6.4093 (13) Å, b = 8.2898 (17) Å, c = 9.3656 (19) Å, and β = 101.51 (3)° for Sr(3)B(6)O(11)F(2) and a = 6.5572 (13) Å, b = 8.5107 (17) Å, c = 9.6726 (19) Å, and β = 101.21 (3)° for Ba(3)B(6)O(11)F(2). The structure consists of a complex triple-ring borate framework having aligned triangular [BO(3)] groups that impart polarity. Fluorine atoms are bound only to the alkaline-earth metals and are not part of the borate framework, resulting in a vastly different structure from those of the hydrated borates Sr(3)B(6)O(11)(OH)(2) and Ba(3)B(6)O(11)(OH)(2) with similar formulas. The title compounds are transparent to nearly 200 nm, making them potentially useful for deep-ultraviolet nonlinear-optical applications.