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. 2009 Jun 1;12(6):583-587.
doi: 10.1016/j.inoche.2009.04.028. Epub 2009 May 7.

Metal-organic frameworks constructed from monomeric, dimeric and trimeric phenanthroline citrate zinc building units

Rong-Hua Zhang  1 , Wen-Sheng Xia, Hong-Xin Wang, Zhao-Hui Zhou
Affiliations

Metal-organic frameworks constructed from monomeric, dimeric and trimeric phenanthroline citrate zinc building units

Rong-Hua Zhang et al. Inorg Chem Commun. .

Abstract

Adduct of mononuclear and dinuclear citrate zinc complex [Zn(Hcit)(phen)(H2O)][Zn2(Hcit)(phen)2(H2O)3]·13.5H2O (1) and its aggregate [Zn3(Hcit)2(phen)4]n·14nH2O (2) (H4cit = citric acid, phen = 1,10-phenanthroline) were synthesized in weak acidic solutions. The former was obtained from the reaction of zinc nitrate, citric acid and phenanthroline in a molar ratio of 3 : 2 : 3, while a slightly excess of phenanthroline results in the formation of the polymeric product 2 in a molar ratio of 3 : 2 : 4. Transformation of 1 to 2 was finished by the reaction of 1 with an equimolar of phenanthroline in 72% yield. Reverse conversion of 2 to 1 is obtained in 77% yield, showing an equilibrium between 1 and 2. Neutral compound 1 consists of one monomeric anionic unit [Zn(Hcit)(phen)(H2O)]- and one dimeric cationic unit [Zn2(Hcit)(phen)2(H2O)3]+ that connect each other by strong hydrogen bonds [O6⋯O4w 2.636(2); O7⋯O3w 2.630(3) Å]. In 2, the citrate ligand links each trinuclear unit [Zn3(Hcit)2(phen)4] to generate an infinite 1D chain that extents into a 3D supramolecular structure by intra- and inter-molecular hydrogen bonds. Moreover, 1 and 2 exhibit strong fluorescence at room temperature.

Keywords: Citric acid; Crystal structure; Interconversion; Mixed ligands; Zinc.

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Figures

Fig. 1a
Fig. 1a
ORTEP plot of the monomeric anionic unit [Zn(Hcit)(phen)(H2O)]–(1a) at the 30% probability level.
Fig. 1b
Fig. 1b
ORTEP plot of the dimeric cationic unit [Zn2(Hcit)(phen)2(H2O)3]+(1b) at the 30% probability level.
Fig. 2a
Fig. 2a
ORTEP plot of the unit in [Zn3(Hcit)2(phen)4]n·14nH2O (2) at the 30% probability level.
Fig. 2b
Fig. 2b
View of the helical chains in 2 along b-axis.
Fig. 3
Fig. 3
Solid-state emission spectra of 1 and 2 at room temperature.
Scheme 1
Scheme 1
Interconversion between 1 to 2.
See this image and copyright information in PMC

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