Dimensional Reduction From 2D Layer to 1D Band for
Germanophosphates Induced by the “Tailor Effect” of
Fluoride
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Abstract
The “tailor effect”
of fluoride, exclusively as a terminal rather than a bridge, was applied
successfully to design low-dimensional structures in the system of
transition metal germanophosphates for the first time. Two series
of new compounds with low-dimensional structures are reported herein.
K[<i>M</i><sup>II</sup>Ge(OH)<sub>2</sub>(H<sub>0.5</sub>PO<sub>4</sub>)<sub>2</sub>] (<i>M</i> = Fe, Co) possess
flat layered structures built from single chains of edge-sharing <i>M</i><sup>II</sup>O<sub>6</sub> and GeO<sub>6</sub> octahedra
interconnected by HPO<sub>4</sub> tetrahedra. Their fluorinated derivatives,
K<sub>4</sub>[<i>M</i><sup>II</sup>Ge<sub>2</sub>F<sub>2</sub>(OH)<sub>2</sub>(PO<sub>4</sub>)<sub>2</sub>(HPO<sub>4</sub>)<sub>2</sub>]·2H<sub>2</sub>O (M = Fe, Co), exhibit band structures
of two four-membered ring germanium phosphate single chains sandwiched
by M<sup>II</sup>O<sub>6</sub> octahedra via corner-sharing. Both
of these structures contain anionic chains of the condensation of
four-membered rings built from alternating GeO<sub>4</sub>Φ<sub>2</sub> (Φ = F, OH) octahedra and PO<sub>4</sub> tetrahedra
via sharing common GeO<sub>4</sub>Φ<sub>2</sub> (Φ = F,
OH) octahedra, the topology of which is the same as that of the mineral
kröhnkite [Na<sub>2</sub>Cu(SO<sub>4</sub>)<sub>2</sub>·2H<sub>2</sub>O]. Note that the switch from the two-dimensional layered
structure to the one-dimensional band structure was performed simply
by the addition of a small amount of KF·2H<sub>2</sub>O to the
reaction mixture. This structural alteration arises from the incorporation
of one terminal F atom to the coordination sphere of Ge, which breaks
the linkage between the transition metal and germanium octahedra in
the layer to form the band structure
