Diversifying molecular and topological space via a supramolecular solid-state synthesis: a purely organic mok net sustained by hydrogen bonds

Abstract

A three-dimensional hydrogen-bonded network based on a rare mok topology has been constructed using an organic molecule synthesized in the solid state. The molecule is obtained using a supramolecular protecting-group strategy that is applied to a solid-state [2+2] photodimerization. The photodimerization affords a novel head-to-head cyclo-butane product. The cyclo-butane possesses tetrahedrally disposed cis-hydrogen-bond donor (phenolic) and cis-hydrogen-bond acceptor (pyridyl) groups. The product self-assembles in the solid state to form a mok network that exhibits twofold interpenetration. The cyclo-butane adopts different conformations to provide combinations of hydrogen-bond donor and acceptor sites to conform to the structural requirements of the mok net.

Keywords: [2+2] photo­cyclo­addition; co-crystals; crystal engineering; intermolecular interactions; organic solid-state reactions; supramolecular chemistry; three-dimensional hydrogen-bonded organic networks.

Figure 1

Post-installation of phenolic groups.

Figure 2

X-ray structure of photostable 1b: (a) hydrogen-bonded chains and (b) stacked C=C bonds of nearest-neighbour alkenes.

Figure 3

X-ray structures of 1c and (diI-res)·2(1c): (a) edge-to-face forces of 1c, (b) C=C bond interactions of nearest-neighbour alkenes of 1c, (c) hydrogen-bonded three-component assembly (diI-res)·2(1c) (top) with C=C separations (bottom) and (d) two-dimensional sheets of (diI-res)·2(1c).

Figure 4

X-ray structure of (diI-res)·(1d): (a) hydrogen bonds and (b) I⋯O halogen bonds.

Figure 5

X-ray structure of 1a: (a) anti–gauche 1a (CB1) and (b) syn–anti 1a (CB2). Note: anti and syn are designated relative to the pyridyl groups.

Figure 6

X-ray structure of mok topology of 1a: (a) interpenetration of hexagonal (hcb) sub-nets highlighted in green and blue, (b) building blocks of cyclo­butanes as nodes to form hydrogen-bonded hexagons numbered in a clockwise manner (hydrogens removed for clarity), (c) connections of two hcb nets (connection highlighted in orange and hcb nets in blue/green), and (d) twofold interpenetrated mok nets highlighted separately in tan and blue.

Figure 7

Hydrogen bonding and rings of mok net 1a: (a) three linkages with CB1 and CB2 (light blue = syn linkage; dark blue = anti linkage; orange = gauche linkage) of a primary six-membered ring, (b) space-filling of primary six-membered ring, (c) primary six-membered ring showing linkages within hcb subnet, (d) two types of linkages of a secondary six-membered ring, (e) space-filling view of secondary six-membered ring, (f) highlighted secondary six-membered ring within mok net, (g) three types of linkages within an eight-membered ring, (h) stick-view of eight-membered ring with anti-orientation from CB1, and (i) space-filling of eight-membered ring showing two interdigitated hcb subnets (hydrogen atoms omitted for clarity).