Series of Luminescent Lanthanide MOFs with Regular SHG Performance

Second-harmonic generation (SHG) is a kind of nonlinear optical phenomenon which has been widely used in optical devices, and factors influencing its signal are very complex. Here, taking advantage of excellent structural designability and overcoming the limitations of various coordinations of lanthanide metals, for the first time a series of lanthanide metal-organic frameworks (Ln-MOFs) with one particular ligand were synthesized and structurally characterized to study the interference of the SHG signal. The optical performance including single-photon fluorescence and SHG was collected and analyzed. It is found that all 13 kinds of Ln-MOFs can be divided into 2 crystal configurations by their individual space groups and Ln-MOFs with coordinated metal atoms from La to Tb possessing the noncentrosymmetric C2 space group exhibit the SHG property, the intensity of which depends on the type of metal atoms, the pumping wavelength, and the size of the single-crystal particles. This is the first time that the relationship between the nonlinear optical properties and the structure, metal atoms, pumping wavelength, crystal size of the whole series of Ln-MOFs is studied systematically, providing a lot of interesting results and enriching the research scope of nonlinear optics and materials science.

A cobalt(II) coordination polymer constructed with the 2-carboxy-phenoxyacetate linker showing a corrugated layer structure: synthesis, structure analysis and magnetic properties

A new binary CoII coordination polymer, [Co(2-cpa)2(H2O)] n (1) has been synthesized by a hydrothermal reaction of cobalt(II) acetate tetrahydrate and 2-carboxy-phenoxyacetic acid (2-H2cpa) in the presence of potassium hydroxide. Structural analysis revealed that the central CoII ion is in an octahedral geometry coordinated with one aqua and five oxygen atoms of three 2-carboxy-phenoxyacetate (2-cpa) ligands. The 2-cpa anions function as pentadentate double bridging chelate-μ 3 linkers binding neighboring CoII ions together, to form an unusual corrugated (4,4)-connected layer. Variable-temperature magnetic susceptibility data in the 2–300 K temperature range indicates a weak antiferromagnetic coupling between adjacent cobalt(II) ions.

Ln(iii)–Ni(ii) heteropolynuclear metal organic frameworks of oxydiacetate with promising proton-conductive properties

Heteropolynuclear metal organic frameworks (MOFs) of the general formula [Ln₂Ni₃(oda)₆(H₂O)₆]·xH₂O (oda = oxydiacetate, Ln = +3 rare earth ion) were synthesized and characterized.