Pb9O4(BO3)2(NO3)4: A Lead Borate–Nitrate Containing an Anion-Centered [O8Pb18]∞ Chain with Large Optical Anisotropy

In the field of structural chemistry, crystals containing the [OM4] tetrahedra (M = metal cation) structure have been well documented. However, compounds containing both [OPb4] tetrahedra and π-conjugated groups are less reported due to their structural complexity. In this work, a new lead borate–nitrate, Pb9O4(BO3)2(NO3)4, has been synthesized by a high temperature melt method. Notably, the structure of Pb9O4(BO3)2(NO3)4 contains special [O8Pb18]∞ chains formed by the [OPb4] tetrahedra. This compound possesses a large optical anisotropy with birefringence of Δn = 0.117 at 546 nm.