Anion-controlled dielectric behavior of homochiral tryptophan-based metal-organic frameworks

Shruti Mendiratta, Muhammad Usman, Tzuoo Tsair Luo, Bor Chen Chang, Shang Fan Lee, Ying Chih Lin, Kuang Lieh Lu

Research output: Contribution to journalArticlepeer-review

46 Scopus citations

Abstract

Three homochiral metal-tryptophanate frameworks, {[Zn2(L-trp) 2(bpe)2(H2O)2]·2H 2O·2NO3}n (1a, L-Htrp = L-tryptophan, bpe = 1,2-bis(4-pyridyl)ethylene), {[Co(L-trp)(bpe)(H2O)] ·H2O·NO3}n (1b), and {[Co(L-trp)(bpa)(H2O)]·H2O·NO 3}n (2, bpa = 1,2-bis(4-pyridyl)ethane), were constructed from Zn2+ or Co2+ ions, bipyridyl ligands, and the amino acid L-tryptophan (L-Htrp), respectively. Compounds 1a, 1b, and 2 were characterized by single-crystal X-ray diffraction analysis. All of the compounds crystallize in the monoclinic space group P21 and form homochiral two-dimensional (2D) layers with rectangle-like (4,4) topologies. Anion-controlled dielectric, luminescence, and nonlinear-optic (NLO) properties were measured for these chiral metal-organic frameworks (MOFs) in the solid state. Emission spectra confirmed that compound 1a exhibited a green emission at 546 nm. Dielectric studies of 1a revealed that it had very low dielectric constant (κ = 2.53 at 1 MHz), thus verifying that it is a promising candidate for interlayer dielectrics. The anion-controlled dielectric properties of 1a were observed after treatment with solutions of different anions. The results revealed a significant change in κ value in the case of the phosphate anion. Secondary harmonic generation (SHG) studies revealed that 1a had a good SHG intensity response that was about twice that of SiO2.

Original languageEnglish
Pages (from-to)1572-1579
Number of pages8
JournalCrystal Growth and Design
Volume14
Issue number4
DOIs
StatePublished - 2 Apr 2014

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