Relationship between Channel and Sorption Properties in Coordination Polymers with Interdigitated Structures

Abstract

Porous coordination polymers constructed from Zn(2+) and isophthalate with linear bipyridyl-type ligands were synthesized. [Zn(ip)(bpb)](n) (CID-21; ip=isophthalate, bpb=1,4-bis(4-pyridyl)benzene), [Zn(ip)(bpt)](n) (CID-22; bpt=3,6-bis(4-pyridyl)-1,2,4,5-tetrazine), and [Zn(ip)(bpa)](n) (CID-23; bpa=1,4-bis(4-pyridyl)acetylene) all have interdigitated structures of layers and similar void volumes (≈27%). In these compounds, 1D bottleneck-type channels run along the perpendicular direction of the layer stacking and their properties are strongly dominated by the dipyridyl linker ligands. Because of the difference in packing of 2D layers, CID-21 and CID-22 have relatively rigid porous structures, whereas CID-23 has greater flexibility, as indicated by the results of powder X-ray diffraction studies. The micropores of CID-22 surrounded by tetrazine moieties adsorb polar molecules, such as methanol and water. The higher affinity of CID-22 for water than CID-21 is supported by a theoretical study. The 1D channel of CID-23 is wider than that of the other two compounds, which enables the incorporation of aromatic molecules. This is because the shape of the bpa linker ligand generates a wider pore diameter (8.6 Å). Only CID-23 can adsorb a benzene molecule and the isotherm of benzene has a gate-opening-type profile. This offers proof of the guest accommodation process through large structural transformation from a nonporous to a porous structure. The flexibility and restricted pore space of CID-23, at 298 K, allows only benzene, but not cyclohexane, to enter the channels. The porous structure exhibits clear selectivity for these similar guests. The incorporation of an elongated dipyridyl linker ligand in the 2D coordination layers provides a strategy for the design of microporous compounds with different flexibilities, microporous environments, and separation abilities.

Incorporating the Thiazolo[5,4-d]thiazole Unit into a Coordination Polymer with Interdigitated Structure

“…Afterwards, the sample was degassed at 120 • C for 15 h under vacuum. The activated compound [Zn(1,3-BDC)Dptztz] shows no uptake of N 2 at 77 K, which is in accordance with the observations by Kitagawa et al for analogous CID structures [24][25][26][27][28][29]. For CO 2 -with its large polarizability and quadrupole moment-[Zn(1,3-BDC)Dptztz] shows a type I adsorption isotherm at 195 K with a maximum uptake of 138 cm 3 /g at 753 mmHg of CO 2 (Figure 7).…”

“…The 2D layers assemble through π-π interactions between isophthalate aryl rings and CH-π interactions between an isophthalate and a pyridyl-moiety of Dptztz of adjacent layers into a 3D supramolecular network (Figure 5c and Figure S3, Table S1). The 2D network in [Zn(1,3-BDC)Dptztz] is isotopic to the aforementioned CIDs (coordination polymers with interdigitated structure) studied by Kitagawa and co-workers [24][25][26][27][28][29]. Table 2 for selected bond lengths and angles.…”

“…CIDs consist of an angular ligand (e.g., isophthalate, benzophenone-4,4 -dicarboxylate, azulene-1,6-dicarboxylate) and a 4,4 -bipyridine derivative and divalent transition metal ions. CIDs show very intriguing sorption properties due to their potential for functionalization and often inherent structural flexibility [24][25][26][27][28][29].…”

Coordination pillared layers using a dinuclear Mn(V) complex as a secondary building unit

“…hydrothermal synthesis. Modification of the components with different organic ligands and metal ions is often applied to enhance the properties of PCP [17][18][19][20][21][22]; however, it is difficult to forecast the resultant structures by the one-pot approach. To solve the problem, a post-synthetic method and a layer-by-layer method for constructing modified frameworks as hierarchical approaches have been developing recently [23][24][25][26][27][28][29].…”

Synthesis and electrochemical properties of an interdigitated architecture based on Keggin phosphotungstates

“…Entanglement compounds such as catenanes, rotaxanes, interdigitation and molecular knots, in which the components are held together by mechanical linkages rather than by covalent bonds, have attracted considerable attention due to not only their abundant architectures and topologies [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16], but also potential applications ranging from catalysis, drug-delivery vehicles to sensor devices [17][18][19][20]. Among the entanglement compounds, interdigitation framework featured by gear-like (or tongue-and-groove) pattern is an intriguing subset, http://dx.doi.org/10.1016/j.molstruc.2014.01.065 0022-2860/Ó 2014 Elsevier B.V. All rights reserved.…”