Photoluminescence Properties of Two Closely Related Isostructural Series Based on Anderson-Evans Cluster Coordinated With Lanthanides [Ln(H2O)7{X(OH)6Mo6O18}]•yH2O, X = Al, Cr

Abstract

The paper describes synthesis and structural characterization of the whole series of two closely related lanthanide coordinated chromium or aluminum hexamolybdates (Anderson-Evans cluster) including twelve new members hitherto unreported: [Ln(H2O)7{X(OH)6Mo6O18}]·4H2O and [Ln(H2O)7{X(OH)6Mo6O18}Ln(H2O)7]{X(OH)6Mo6O18}·16H2O where X = Al or Cr and Ln = La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, and Y. Crystal structures of all the solids were established by powder and single crystal X-ray diffraction techniques. The two series are dictated by a different aggregation of the same set of molecular species: Lighter lanthanides favor coordination interaction between lanthanide ions and molybdate cluster forming 1D chains (Series I) while the heavier lanthanides result in the stacking of a cation, a pair of lanthanide hydrates coordinating to the cluster, and an anion, the discrete cluster is further stabilized through a large number of water molecules (Series II). Crystallization with Er3+ and Tm3+ ions results in a concomitant mixture of Series I and II. Photoluminescence of single crystals of all the chromium molybdates was dominated by a ruby-like emission including those which contain optically active ions Pr, Sm, Eu, Tb, Dy, and Tm. In contrast, aluminum analogs showed photoluminescence corresponding to characteristic lanthanide emissions. Our results strongly suggest a possible energy transfer from f levels of lanthanide ions to d levels of chromium (III) causing the quenching of lanthanide emission when coordinated with chromium molybdates. Intensity measurements showed that the emission from chromium molybdates are almost two orders of magnitude lower than naturally occurring ruby with broader line widths at room temperature.

Synthesis and Characterization of New Anderson-Type Polyoxometalates: [M((1,10-phen)(OH)x]3[Cr(OH)6Mo6O18]·16H2O (M=Cr, Mn, Co, Ni, Cu; x=1,2)

“…The absorption band at 410-422 cm -1 is attributed to the Cr-O. FT-IR results are in agreement with those from previous studies (20)(21)(22)(25)(26).…”

“…Thus, it was determined that the structures of these newly synthesized compounds were similar to the previously reported compounds. (21,22,25,26).…”

Synthesis and Characterization of Ammonium Potassium Tellurium Polyoxomolybdate: (NH4)2K2TeMo6O22·2H2O with One-Dimensional Anionic Polymeric Chain [TeMo6O22]4−

“…The later crystallizes in the [Mo 6 Te 2 O 24 ] 4− zerodimensional aggregates composed of one hexamolybdic Mo 6 O 18 and two discrete TeO 3 units. Anderson-Evans polyoxometalates (POMs) containing heteroatom tellurium are known as one of the pioneering POM archetypes, which usually exist as a discrete [TeMo 6 O 24 ] 6− cluster in the crystal structures [20][21][22][23][24][25][26][27][28][29][30]. Polyoxometalates with one-dimensional chain-like, two-dimensional layer-like, or three-dimensional anionic extended framework structures are relatively rare.…”

In Vitro Anti-tumoral and Anti-bacterial Activity of an Octamolybdate Cluster-Based Hybrid Solid Incorporated with a Copper Picolinate Complex

“…In this context, polyoxometalates (POMs) have been found to be promising anti-tumor agents in the last few decades. , POMs are a kind of discrete oxygen cluster anions constructed by transition metals of group 5 and group 6 (V, Nb, Ta, Mo, and W) . Owing to the great diversity in structures and properties, POMs have shown a wide range of applications in different fields including catalysis, , electrochemistry, materials science, − macromolecular crystallography, biotechnology, nanotechnology, and medicine. , Over the last decade, studies on their applications in the medicinal field have established the importance of POMs as drug candidates with remarkable anti-viral, anti-bacterial, and anti-tumoral activities. , Yamase and co-workers showed in vitro and in vivo anti-cancer activities of [NH 3 Pri] 6 [Mo 7 O 24 ] (PM-8) proving it to be a major development for POMs as anti-tumor agents. , Yamase also proposed a single-electron mechanism for the inhibitory effect of POMs against cancers . Despite the remarkable potential shown by purely inorganic POMs against several cancer types, their clinical application is hindered by their long-term cytotoxicity.…”