The First Two-Dimensional Polycatenane:  A New Type of Robust Network Obtained by Ag-Connected One-Dimensional Polycatenanes

Abstract

ABSTRACT:The two-dimensional structure described here is the first example of a coordination polymer structure consisting of onedimensional polycatenanes fused via silver ions. It can be derived from simple rings consisting of two silver ions and two ligand molecules.In the past decade, metal-organic frameworks (MOFs) have turned out to be a fascinating pool for structure design, synthesis, and applications in numerous fields such as catalysis, magnetism, luminescence, or gas storage. 1 By judicious choice of the building units, (i) the ligand concerning rigidity, form, and donor functions and (ii) the metal ion with its capacity to accept coordination by a given number of ligands, low-dimensional frameworks can be designed and constructed. 2 However, polymorphism and supramolecular isomerism occur more frequently the more flexible both building blocks are. 3 Porous frameworks with large empty spaces are a big challenge as interpenetration can occur. 4 We are interested in using a flexible system with a metal ion such as Ag + and a multitopic ligand Ln (n ) 1, 2 ...) (Scheme 1) with N-and O-donor atoms to synthesize adaptable MOFs, which are able to link a second metal ion type. With the shorter ligand L1, n ) 1, a number of one-dimensional (1D) structural motifs could be characterized, 5-7 whereas with L2, a zero-dimensional metallacycle with two Ag + ions and two L2 molecules, as well as a 1D helix, could be reported. 8 Whereas with this ligand type Ln and Ag + , only coordination numbers of two for Ag + with respect to the nitrogen atoms of Ln were reported so far; 6-9 we now report a new type of network derived from the polycatenation of a 1D chain of fused metallacycles in which Ag + has a coordination number of four with respect to L2. The obtained structure is an unprecedented example of linked polycatenane chains to give a very robust two-dimensional (2D) network of high density.Results and Discussion. The reaction of L2 with AgClO 4 in the ratio 1:1 yields the 2:2 metallacycle or a 1D helix as a supramolecular isomer. 8 With AgPF 6 , exo-linked 2:2 metallacycles of the composition [Ag(L2)] 2 (PF 6 ) 2 ‚THF (1) (THF ) tetrahydrofuran) are obtained. The ratio L2/Ag + of 2:1 yields, after a long reaction time of over two months, a very dense and highly catenated structure of composition [Ag(L2) 2 ](PF 6 ) (2) representing a missing link in polycatenation motifs.1 crystallizes in the triclinic space group P1 h (No. 2), 15 with one molecule per unit cell. Two ligands L2 adopt a U-shape and coordinate to two metal ions to yield a cyclic structure, with Ag-N distances of 2.136(4) and 2.143(4) Å, and an N1-Ag-N2 angle of 169.31(19)° (Figure 1). The two PF 6 -anions bridge two silver ions belonging to the same ring; the Ag-F bonds are weak with distances of 2.960(7) and 3.092(5) Å. Because of this arrangement, the Ag-Ag distance within the ring is rather long at 5.213(13) Å, and π-stacking within the ring is thus excluded with pyridine rings offset from each other by 5.1218 Å.The rings in 1 are arranged parallel...

Rings, chains and helices: new antimicrobial silver coordination compounds with (iso-)nicotinic acid derivatives

“…27 It can act as a bridge between metal cations, 27 or it can approach and connect structural motifs that otherwise would be independent. 25 The CF 3 SO 3 − ion belongs to the anion type that can act in a polydentate or monodentate fashion. In 3, the oxygen atom (O7) of the CF 3 SO 3 − anion not only coordinates to the metal cation, but is also involved in H-bonding with H1 and H14 (C1-H1⋯O7, 2.68 Å and C14-H14⋯O7, 2.49 Å).…”

An infinite chainmail of M6L6 metallacycles featuring multiple Borromean links

“…Coordination polymers are crystalline assemblies of metal cations and bridging organic ligands with infinite 2D or 3D network structures. Whole coordination networks may be entangled through interpenetration or polycatenation, [21][22][23] and infinite networks have been reported to form through catenane formation between chemically independent rings 24,25 catenane formation between 1D coordination polymers, 26 or between 3D metallo-cages. 27,28 A Borromean ring or link is composed of three independent rings that are linked together but where no two rings are interlocked into a catenane.…”

“…Such a network has been envisaged through infinite [2]catenane links 23 but the closest examples have been [2]catenane infinite chains of metallacycles (0D to 1D), 24,25 and a 2D network where coordination chains of fused metallacycles link together through catenane formation (1D to 2D). 26 Polycatenation also occurs in organic polymers and oligomers. 39,40 Catenane chainmail motifs do occur in biology, notably in viral capsids.…”

Silver coordination polymers with isonicotinic acid derived short polyethylene glycol – Synthesis, structures, anion effect and solution behavior

“…These oligomers were found to be mixtures of + m/z [12]. Table 1 gives the relative percentage of each species as a function of metal to ligand ratio as well as time.…”

“…We started to investigate silver coordination polymers using the neutral ligand ethanediyl bis(isonicotinate) Li1 (Scheme 1) [9,10] and its derivatives, which can be modified by simple elongation of the middle spacer, using diethylene glycol [11], triethylene glycol [12,13] and tetraethylene glycol [13,14] as starting materials for the synthesis of the ligands. In this manuscript however, we will focus on the shortest variant of the ligand, Li1.…”