Molecular
Indium(III) Phosphonates Possessing Ring and Cage Structures. Synthesis
and Structural Characterization of [In<sub>2</sub>(<i>t</i>‑BuPO<sub>3</sub>H)<sub>4</sub>(phen)<sub>2</sub>Cl<sub>2</sub>] and [In<sub>3</sub>(C<sub>5</sub>H<sub>9</sub>PO<sub>3</sub>)<sub>2</sub>(C<sub>5</sub>H<sub>9</sub>PO<sub>3</sub>H)<sub>4</sub>(phen)<sub>3</sub>]·NO<sub>3</sub>·3.5H<sub>2</sub>O
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Abstract
Two
novel indium(III) phosphonates, [In<sub>2</sub>(<i>t</i>-BuPO<sub>3</sub>H)<sub>4</sub>(phen)<sub>2</sub>Cl<sub>2</sub>]
(<b>1</b>) and [In<sub>3</sub>(C<sub>5</sub>H<sub>9</sub>PO<sub>3</sub>)<sub>2</sub>(C<sub>5</sub>H<sub>9</sub>PO<sub>3</sub>H)<sub>4</sub>(phen)<sub>3</sub>]·NO<sub>3</sub>·3.5H<sub>2</sub>O (<b>2</b>) with phen = 1,10-phenanthroline, have been synthesized
by solvothermal reactions involving indium(III) salts and organophosphonic
acids. <b>1</b> is a dinuclear compound where the two indium
centers are bridged by a pair of isobidentate phosphonate ligands,
[<i>t</i>-BuP(O)<sub>2</sub>OH]<sup>−</sup>, resulting
in an eight-membered (In<sub>2</sub>P<sub>2</sub>O<sub>4</sub>) puckered
ring. Compound <b>2</b> is trinuclear; the In<sub>3</sub> platform
is held together by two bicapping tripodal phosphonate ligands from
the top and bottom of the indium plane. In addition, two bridging
monoanionic phosphonate ligands serve to bind two pairs of indium
centers. Both <b>1</b> and <b>2</b> also contain monodentate
monoanionic phosphonate ligands. The solid-state MAS <sup>31</sup>P NMR spectrum of complex <b>1</b> shows two signals at 21.9
and 29.3 ppm. Compound <b>2</b> contains signal maxima at 25.8
and 28.9 ppm, with a shoulder at 31.5 ppm. Room temperature solid-state
fluorescence spectra of <b>1</b> and <b>2</b> are characterized
by strong emission bands at 385 nm (λ<sub>ex</sub> = 350 nm)
and 395 nm (λ<sub>ex</sub> = 350 nm), respectively, which are
red-shifted with respect to the emission of free phenanthroline
