Na 2 (H 2 en)[B 5 O 8 (OH)] 2 [B 3 O 4 (OH)] 2 and Na 3 (HCOO)[B 5 O 8 (OH)]: Two Borates Co‐Templated by Inorganic Cations and Organic Compounds

The cooperative effect of inorganic and organic co‐templates led to two layered borates: centrosymmetric (CS) Na 2 (H 2 en)[B 5 O 8 (OH)] 2 [B 3 O 4 (OH)] 2 ( 1 ; en = ethylenediamine) and noncentrosymmetric (NCS) Na 3 (HCOO)[B 5 O 8 (OH)] ( 2 ). Compound 1 features coupled layers extended by two different oxoboron clusters, which are rare in borates. The Na + cations are located in the channel and hold the coupled layers in tight inorganic B–O–Na layers, while H 2 en 2+ cations reside in channels between inorganic layers. Compound 2 is the first NCS borate directed by inorganic and organic species simultaneously and features acentric [B 5 O 8 (OH)] n 2 n – layers. It exhibits a good second harmonic generation efficiency of about 1.9 times that of potassium dihydrogenphosphate and is phase‐matchable, and the UV cutoff edge below 200 nm makes 2 a potential UV nonlinear optical material. Investigation of the fluorescence properties indicated that the new borates are potential blue fluorescent materials. In addition, structure elucidation revealed that host–guest symmetry matching plays a key role in the formation of CS 1 and NCS 2 .