Amine-Templated Aluminoborates Exhibiting Graphite and Diamond Nets

A solvothermal reaction of Al 2 O 3, H 3 BO 3, pyridine, and H 2 O at 180 °C/7 days in the presence of organic amine molecules gave rise to four new aluminoborates, [(C 6 H 18 N 2 )(AlB 6 O 13 H 3 )], I; [(C 5 H 16 N 2 )(AlB 5 O 10 )]·2H 2 O, II; [(C 5 H 16 N 2 )(AlB 5 O 10 )], III; and [(C 5 H 17 N 3 )(AlB 5 O 10 )]·H 2 O, IV, with two- and three-dimensional structures. All the structures have been formed by the connectivity involving Al 3+ ions and [B 5 O 10 ] cyclic pentaborate units. In I, the 3-connected trigonal nodes form a layer that resembles a graphite structure has been observed. The compounds II, III, and IV, have 4-connected nodes that forms a diamond related three-dimensional structure. The formation of solvatomorphs in II and III is noteworthy and has been observed first time in a family of amine templated aluminoborates. A comparison of the various aluminoborate structures reveals subtle relationships between the organic amines (length of the amines) and the final framework structures. The compounds have been characterized using a variety of techniques including IR, second-order optical behavior, and MAS NMR studies.