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Updated: May 13, 2026

Experimental Approaches for the Synthesis of Low-Valent Metal-Organic Frameworks from Multitopic Phosphine Linkers
Published on: May 12, 2023
Metal-organic frameworks constructed from monomeric, dimeric and trimeric phenanthroline citrate zinc building units
Rong-Hua Zhang1, Wen-Sheng Xia, Hong-Xin Wang
1College of Chemistry and Chemical Engineering, State Key Laboratory of Physical Chemistry of Solid Surface, National Engineering Laboratory for Green Chemical Productions of Alcohols-Ethers-Esters, Xiamen University, Xiamen 361005, China.
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.
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