Issue 34, 2015

Manipulating connecting nodes through remote alkoxy chain variation in coordination networks with 4′-alkoxy-4,2′:6′,4′′-terpyridine linkers

Abstract

The effects of increasing the length of the alkoxy substituent in 4′-alkoxy-4,2′:6′,4′′-terpyridines when they are combined with cadmium(II) nitrate under conditions of room temperature crystallization and in the same cadmium : ligand (1 : 3) ratio have been investigated. The divergent ligand 4′-n-propoxy-4,2′:6′,4′′-terpyridine (2) reacts with Cd(NO3)2·4H2O to give [{Cd2(NO3)4(2)3}·3CHCl3]n in which the Cd atoms act as 3-connecting nodes and assemble into a (6,3) net with each ligand 2 linking adjacent Cd atoms. One of the three independent n-propoxy groups nestles into a cleft in the next 2-dimensional sheet; this ‘tail-in-pocket’ interaction restricts the length of the alkyl chain that can be accommodated. Replacing the n-propoxy by an n-pentoxy, n-hexoxy or n-heptoxy substituent results in a switch from a (6,3) to (4,4) net; in [{Cd2(NO3)4(3)4}·3CHCl3]n (3 = 4′-n-pentoxy-4,2′:6′,4′′-terpyridine) and [{Cd2(NO3)4(4)4}·CHCl3·MeOH]n (4 = 4′-n-hexoxy-4,2′:6′,4′′-terpyridine), each Cd atom is a 4-connecting node with trans-nitrato ligands, while in [{Cd(NO3)2(5)2}·2MeOH]n (5 = 4′-n-heptoxy-4,2′:6′,4′′-terpyridine) a cis-arrangement of nitrato ligands is observed. The reaction between Cd(NO3)2·4H2O and 4 was also investigated using a 1 : 1 ratio of reagents; this leads to the assembly of the 1-dimensional ladder [Cd2(NO3)4(MeOH)(4)3]n in which each Cd atom is a 3-connecting node. In each structure, face-to-face π-stacking of the central pyridine rings or of pyridine/phenyl rings of ligands in adjacent sheets or chains is a primary packing interaction; the role of van der Waals interactions as the chain length increases is discussed. Powder diffraction confirmed that each coordination polymer or network characterized by single crystal X-ray crystallography was representative of the bulk sample. The solid-state emission properties of ligands 2, 3 and 4 and their coordination polymers are reported; the blue emission of the free ligands is red-shifted by up to 59 nm upon formation of the coordination networks, and quantum yields are in the range 11–22%.

Graphical abstract: Manipulating connecting nodes through remote alkoxy chain variation in coordination networks with 4′-alkoxy-4,2′:6′,4′′-terpyridine linkers

Supplementary files

Article information

Article type
Paper
Submitted
08 Jun 2015
Accepted
26 Jun 2015
First published
06 Jul 2015
This article is Open Access
Creative Commons BY license

CrystEngComm, 2015,17, 6483-6492

Author version available

Manipulating connecting nodes through remote alkoxy chain variation in coordination networks with 4′-alkoxy-4,2′:6′,4′′-terpyridine linkers

Y. M. Klein, A. Prescimone, E. C. Constable and C. E. Housecroft, CrystEngComm, 2015, 17, 6483 DOI: 10.1039/C5CE01115A

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