Probing the Self-Assembly Mechanism of Lanthanide-Containing Sandwich-Type Silicotungstates [{Ln(H2O)n}2{Mn4(B-α-SiW9O34)2(H2O)2}]6– Using Time-Resolved Mass Spectrometry and X-ray Crystallography

The reaction of [γ-SiW10O36]8– with Mn2+ and Ln3+ in an aqueous solution led to the isolation of a series of new lanthanide-containing sandwich-type polyoxometalates (POMs) [{Ln(H2O)n}2{Mn4(B-α-SiW9O34)2(H2O)2}]6– (1–5a) (Ln = La (1), Nd (2), Gd (3), Dy (4), Er (5); n = 5, 6), which crystallize in the space groups C2/c with a = 33.0900(2)–32.9838(15) A, b = 12.8044(10)–12.7526(6) A, c = 22.8273(17)–22.6368(11) A, V = 9669.2(12)–9519.7(8) A3, Z = 2 (1, 2); P1 with a = 11.9502(4)–11.8447(6) A, b = 13.2203(4)–13.1164(5) A, c = 15.8291(5)–15.8524(7) A, V = 2221.25(13)–2189.95(18) A3, Z = 1 (3, 4, 5), respectively. X-ray diffraction analysis reveals that they consist of two-dimensional networks based on a sandwich-type polyanion [Mn4(B-α-SiW9O34)2(H2O)2]12– (6a, {Mn4(SiW9)2}) and lanthanide cations (Ln3+), which are further connected into three-dimensional frameworks by potassium cations for 3, 4, and 5. The unprecedented combination of time-resolved electrospray ionization mass spectrometry (ESI-MS) studies ...