A [4+2] Condensation Strategy to Imine-Linked Single-Crystalline Zeolite-Like Zinc Phosphate Frameworks

作者：Jangir Ritambhara; Kalita Alok Ch; Kaleeswaran Dhananjayan; Gupta Sandeep K; Murugavel Ramaswamy

来源：Chemistry - A European Journal, 2018, 24(23): 6178-6190.

DOI：10.1002/chem.201800149

<jats:title>Abstract</jats:title><jats:p>Double‐4‐ring zinc phosphate (D4R), [Zn(dipp)(4‐Py‐CHO)]<jats:sub>4</jats:sub> (<jats:bold>2</jats:bold>) (dipp=diiminopyridine), bearing four formyl groups, has been utilized as a building block (SBU) for the synthesis of a new class of imine‐linked [4+2] COF‐like polycrystalline zinc phosphate frameworks. Reactions of <jats:bold>2</jats:bold> with a series of linear aromatic diamines results in the formation of polycrystalline frameworks [Zn<jats:sub>4</jats:sub>(dipp)<jats:sub>4</jats:sub>(<jats:bold>L</jats:bold>)<jats:sub>2</jats:sub>]<jats:sub><jats:italic>n</jats:italic></jats:sub> (<jats:bold>3</jats:bold>–<jats:bold>6</jats:bold>) (<jats:bold>L</jats:bold>=<jats:bold>L<jats:sup>1</jats:sup></jats:bold> to <jats:bold>L<jats:sup>4</jats:sup></jats:bold>, diimines formed by condensation of 4‐pyridine carboxaldehyde with diamines). Employing an alternative synthetic strategy, through a diffusion‐controlled slow reaction of <jats:bold>2</jats:bold> with the pre‐synthesized 4,4‘‐bispyridyl bisimine (<jats:bold>L<jats:sup>3</jats:sup></jats:bold>), [Zn<jats:sub>4</jats:sub>(dipp)<jats:sub>4</jats:sub>(<jats:bold>L<jats:sup>3</jats:sup></jats:bold>)<jats:sub>2</jats:sub>]<jats:sub><jats:italic>n</jats:italic></jats:sub> (<jats:bold>5′</jats:bold>) has been obtained as single crystals. Complex <jats:bold>5′</jats:bold> is a 3D‐framework, exhibiting a rare eightfold interpenetrated diamondoid network. The long spacer length (19.6 Å) results in extensive entanglement in <jats:bold>5′</jats:bold>. Powder diffraction data suggest that these compounds are isoreticular 3D‐frameworks. To study the effect of the relative position of pyridyl donors with respect to the central benzidine moiety, 3,3‘‐bispyridyl bisimine (<jats:bold>L<jats:sup>5</jats:sup></jats:bold>) was investigated as the spacer. A slow reaction of <jats:bold>1 b</jats:bold> with <jats:bold>L<jats:sup>5</jats:sup></jats:bold> leads to the isolation of a 2D‐boxed‐sheet coordination polymer [Zn<jats:sub>4</jats:sub>(dipp)<jats:sub>4</jats:sub>(<jats:bold>L<jats:sup>5</jats:sup></jats:bold>)<jats:sub>2</jats:sub>]<jats:sub><jats:italic>n</jats:italic></jats:sub> (<jats:bold>7</jats:bold>). Selective formation of 3D‐framework <jats:bold>5′</jats:bold> from <jats:bold>L<jats:sup>3</jats:sup></jats:bold> and the 2D‐framework <jats:bold>7</jats:bold> from <jats:bold>L<jats:sup>5</jats:sup></jats:bold> is due to the angles created by the coordination of <jats:italic>para</jats:italic>‐ and <jats:italic>meta</jats:italic>‐pyridyl nitrogen centers at the zinc centers of the D4R cubane. Compound <jats:bold>5′</jats:bold> has been utilized as a catalyst for Knoevenagel condensation.</jats:p>

• 出版日期2018-4-20