Structural Diversity of the Oxovanadium Organodiphosphonate System: A Platform for the Design of Void Channels

The hydrothermal reactions of a vanadium source, an appropriate diphosphonate ligand, and water in the presence
of HF provide a series of compounds with neutral V−P−O networks as the recurring structural motif. When the
{O3P(CH2)nPO3}4- diphosphonate tether length n is 2−5, metal−oxide hybrids of type 1, [V2O2(H2O){O3P(CH2)nPO3}]·xH2O, are isolated. The type 1 oxides exhibit the prototypical three-dimensional (3-D) “pillared” layer architecture.
When n is increased to 6−8, the two-dimensional (2-D) “pillared” slab structure of the type 2 oxides [V2O2(H2O)4{O3P(CH2)6PO3}] is encountered. Further lengthening of the spacer to n = 9 provides another 3-D structure, type
3, constructed from the condensation of pillared slabs to give V−P−O double layers as the network substructure.
When organic cations are introduced to provide charge balance for anionic V−P−O networks, oxides of types 4−7
are observed. For spacer length n = 3, a range of organodiammonium cations are accommodated by the same
3-D “pillared” layer oxovanadium diphosphonate framework in the type 4 materials [H3N(CH2)nNH3][V4O4(OH)2
{O3P(CH)3PO3}2]·xH2O [n = 2, x = 6 (4a); n = 3, x = 3 (4b); n = 4, x = 2 (4c); n = 5, x = 1 (4d); n = 6,
x = 0.5 (4e); n = 7, x = 0 (4f)] and [H3NR]y[V4O4(OH)2 {O3P(CH)3PO3}2]·xH2O [R = −CH2(NH3)CH2CH3, y =
1, x = 0 (4g); R = −CH3, n = 2, x = 3 (4h); R = −CH2CH3, y = 2, x = 1 (4i); R = −CH2CH2CH3, y = 2, x
= 0 (4j); cation = [H2N(CH2CH3)2], y = 2, x = 0 (4k)]. These oxides exhibit two distinct interlamellar domains,
one occupied by the cations and the second by water of crystallization. Furthermore, as the length of the cation
increases, the organodiammonium component spills over into the hydrophilic domain to displace the water of
crystallization. When the diphosphonate tether length is increased to n = 5, structure type 5, [H3N(CH2)2NH3][V4O4(OH)2(H2O){O3P(CH2)5PO3}2]·H2O, is obtained. This oxide possesses a 2-D “pillared” network or slab structure,
similar in gross profile to that of type 2 oxides and with the cations occupying the interlamellar domain. In contrast,
shortening the diphosphonate tether length to n = 2 results in the 3-D oxovanadium organophosphonate structure
of the type 7 oxide [H3N(CH2)5NH3][V3O3{O3P(CH2)2PO3}2]. The ethylenediphosphonate ligand does not pillar V−P−O
networks in this instance but rather chelates to a vanadium center in the construction of complex polyhedral
connectivity of 7. Substitution of piperazinium cations for the simple alkyl chains of types 4, 5, and 7 provides the
2-D pillared layer structure of the type 6 oxides, [H2N(CH2CH2)NH2][V2O2{O3P(CH)nPO3H}2] [n = 2 (6a); n = 4
(6b); n = 6 (6c)]. The structural diversity of the system is reflected in the magnetic properties and thermal behavior
of the oxides, which are also discussed.

以钒源、适宜的二磷酸酯配体及水在氢氟酸存在下发生的氢热反应，生成了一系列以中性V-P-O网络作为重复结构基元的化合物。当{O3P(CH2)nPO3}4-二磷酸酯的 tether 长度 n 为2−5时，可分离出类型1的金属-氧化物杂化物，即[V2O2(H2O){O3P(CH2)nPO3}]·xH2O。此类氧化物呈现典型的三维（3-D）“柱状”层状结构。当 n 增至6−8时，遇到类型2的二维（2-D）“柱状”板状结构氧化物[V2O2(H2O)4{O3P(CH2)6PO3}]。进一步延长间隔至 n = 9，则提供另一种三维结构，即类型3，由柱状板状结构的缩合形成，其中V-P-O双层作为网络亚结构。引入有机阳离子以平衡阴离子V-P-O网络的电荷，观察到类型4−7的氧化物。对于间隔长度 n = 3，同一三维“柱状”层状氧化钒二磷酸酯框架可容纳多种有机二铵阳离子，构成类型4材料[H3N(CH2)nNH3][V4O4(OH)2 {O3P(CH)3PO3}2]·xH2O [n = 2, x = 6 (4a); n = 3, x = 3 (4b); n = 4, x = 2 (4c); n = 5, x = 1 (4d); n = 6, x = 0.5 (4e); n = 7, x = 0 (4f)]和[H3NR]y[V4O4(OH)2 {O3P(CH)3PO3}2]·xH2O [R = −CH2(NH3)CH2CH3, y = 1, x = 0 (4g); R = −CH3, n = 2, x = 3 (4h); R = −CH2CH3, y = 2, x = 1 (4i); R = −CH2CH2CH3, y = 2, x = 0 (4j); 阳离子 = [H2N(CH2CH3)2], y = 2, x = 0 (4k)]。这些氧化物展现出两个独特的层间域，其中一个被阳离子占据，另一个由结晶水占据。此外，随着阳离子长度的增加，有机二铵组分溢出到亲水域，取代结晶水。当二磷酸酯 tether 长度增至 n = 5时，获得结构类型5的氧化物[H3N(CH2)2NH3][V4O4(OH)2(H2O){O3P(CH2)5PO3}2]·H2O。此氧化物拥有二维“柱状”网络或板状结构，宏观上与类型2氧化物相似，且阳离子占据层间域。相反，缩短二磷酸酯 tether 长度至 n = 2，导致类型7氧化物的三维氧化钒有机磷腈结构[H3N(CH2)5NH3][V3O3{O3P(CH2)2PO3}2]。在此例中，乙二磷酸酯配体并未柱化V-P-O网络，而是与钒中心螯合，构建了7号复杂多面连接结构。以哌嗪阳离子替换类型4、5和7的简单烷基链，提供了类型6氧化物的二维“柱状”层状结构[H2N(CH2CH2)NH2][V2O2{O3P(CH)nPO3H}2] [n = 2 (6a); n = 4 (6b); n = 6 (6c)]。该系统的结构多样性体现在氧化物的磁性和热行为上，亦有所讨论。