How does the synthesis temperature impact hybrid organic-inorganic molybdate material design?

ABSTRACT

We investigate the reactivity of MoO(4)(2-) toward six organoammonium cations (+)(Me(3-x)H(x)N)(CH(2))(2)(NH(y)Me(3-y))(+) (x, y = 1-3) at different synthesis temperatures ranging from 70 to 180 °C. A total of 16 hybrid organic-inorganic materials have been synthesized at an initial pH of 2, via ambient pressure and hydrothermal routes, namely, (H(2)en)[Mo(3)O(10)]·H(2)O (1), (H(2)en)[Mo(3)O(10)] (2), (H(2)en)[Mo(5)O(16)] (3), (H(2)MED)(2)[Mo(8)O(26)]·2H(2)O (4), (H(2)MED)[Mo(5)O(16)] (5), (N,N-H(2)DMED)(2)[Mo(8)O(26)]·2H(2)O (6), (N,N-H(2)DMED)(2)[Mo(8)O(26)]·2H(2)O (7), (N,N'-H(2)DMED)(2)[Mo(8)O(26)] (8), (N,N'-H(2)DMED)[Mo(5)O(16)] (9), (H(2)TriMED)(2)[Mo(8)O(26)]·4H(2)O (10), (H(2)TriMED)(2)[Mo(8)O(26)]·2H(2)O (11), (H(2)TriMED)[Mo(7)O(22)] (12), (H(2)TMED)(2)[Mo(8)O(26)]·2H(2)O (13), (H(2)TMED)(2)[Mo(8)O(26)] (14), (H(2)TMED)(2)[Mo(8)O(26)] (15), and (H(2)TMED)[Mo(7)O(22)] (16). All of these compounds contain different polyoxomolybdate (Mo-POM) blocks, i.e., discrete ß-[Mo(8)O(26)](4-) blocks in 6, 10, 13, 14, (1)/(∞)[Mo(3)O(10)](2-), and (1)/(∞)[Mo(8)O(26)](4-) polymeric chains in 1, 2, 4, 7, 8, and 15, respectively, and (2)/(∞)[Mo(5)O(16)](2-) and (2)/(∞)[Mo(7)O(22)](2-) layers in 3, 5, 9, 12, and 16, respectively. The structures of 5, 9, and 14 have been resolved by single-crystal X-ray analyses. The characterization of the different Mo-POM blocks in 1-16 by Fourier transform Raman spectroscopy is reported. The impact of the synthesis temperature on both the composition and topology of the Mo-POM blocks is highlighted.