A Crystalline Mesolamellar Gallium Phosphate with Zwitterionic-type Templates Exhibiting Green Afterglow Property

We synthesized a unique layer structure
of gallium phosphates containing zwitterionic-type templates under
mild hydrothermal reactions. The zwitterionic-type templates, formed
of long-alkyl-chain diamine cations and biphenyldicarboxylate anions,
resided upright between adjacent layers, propping the interlayer distance
up to 2.2 nm. For the first time, the mesoscale interlayer templates
were sufficiently well-ordered to afford elucidation to the atomic-level.
The mesolamellar (HDADD)2(BPDC)0.5[Ga3(OH)2(HPO4)4] (1; DADD
= 1,12-diaminododecane, BPDC = 4,4′-biphenyldicarboxylate)
was composed of inorganic layers built up exclusively with a unique
type of heptameric unit which featured an unprecedented trimeric cluster
of [Ga3(OH)2O12]. Unexpectedly, compound 1 possessed an unusual green afterglow. To interpret the interesting
photoluminescence (PL) property, three other low-dimensional structures
related to 1 were prepared as well. The data from PL
and electron paramagnetic resonance indicated that the afterglow was
mainly attributed to lattice defects and the orientations of BPDC.