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 cadmiumIJII) 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 CdIJNO 3 ) 2 ·4H 2 O to give ij{Cd 2 IJNO 3 ) 4 IJ2) 3 }·3CHCl 3 ] 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-inpocket' 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 ij{Cd 2 IJNO 3 ) 4 IJ3) 4 }·3CHCl 3 ] n (3 = 4′-n-pentoxy-4,2′:6′,4″-terpyridine) and ij{Cd 2 IJNO 3 ) 4 IJ4) 4 }·CHCl 3 ·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 ij{CdIJNO 3 ) 2 IJ5) 2 }·2MeOH] n (5 = 4′-n-heptoxy-4,2′:6′,4″-terpyridine) a cis-arrangement of nitrato ligands is observed. The reaction between CdIJNO 3 ) 2 ·4H 2 O and 4 was also investigated using a 1 : 1 ratio of reagents; this leads to the assembly of the 1-dimensional ladder ijCd 2 IJNO 3 ) 4 IJMeOH)IJ4) 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 4and 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%. coordination sites 11 or sterically variable substituents (e.g. bulky 12 or long chain, 13,14 alkyl groups) that influence packing interactions and assembly motifs.Although strategies towards 2-and 3-dimensional networks are currently being developed using ditopic 4,2′:6′,4″tpy and its isomeric 3,2′:6′,3″-tpy linkers, 15,16 the coordination chemistry of 4,2′:6′,4″-tpy remains dominated by 1-dimensional chains. This preference can be modified by turning attention to the metal node. For example, linear {Zn 2 IJOAc) 4 } nodes (Scheme 1) combined with 4,2′:6′,4″-tpys CrystEngComm, 2015, 17, 6483-6492 | 6483This journal is

Isomers of Terpyridine as Ligands in Coordination Polymers and Networks Containing Zinc(II) and Cadmium(II)

“…This contrasts with the numerous 1D-polymers that are observed for combinations of zinc(II) salts with 4,2′:6′,4″-tpy ligands with non-coordinating substituents, and highlights the fact that the higher coordination numbers favored by Cd(II) can lead to higher dimensionality assemblies. Similar (4,4)-nets are formed when Cd(NO 3 ) 2 ·4H 2 O, CdBr 2 or CdI 2 reacts with 48 ( Figure 30 a) [ 88 ], or when Cd(NO 3 ) 2 ·4H 2 O combines with 4′-(4-ROC 6 H 4 )-4,2′:6′,4″-tpy in which R = n pentyl, n hexyl, or n heptyl [ 89 ]. However, for smaller R groups, the assembly switches to either a ladder (for R = Me, ligand 49 ) [ 90 ] or a (6,3) net (for R = n propyl) [ 89 ].…”

Synthesis of Terpyridines: Simple Reactions—What Could Possibly Go Wrong?

“…We have shown that in the 4,2′:6′,4″-tpy compounds 4a – k (R = n -C n H 2n+1 , n = 1–10, 12, Figure 2), the length of the alkyl chain on the alkyloxy substituent can influence the packing and the topology of coordination networks generated upon reaction with metal salts [22,25,26,27,28,29,30]. We are now beginning a systematic investigation of the effect of substituents on the assembly of coordination networks based on 3,2′:6′,3″-tpy ligands and commenced with the synthesis of derivatives 5a – c .…”

Constructing chiral MOFs by functionalizing 4,2′:6′,4′′-terpyridine with long-chain alkoxy domains: rare examples of neb nets

“…[16][17][18] or Cd(NO 3 ) 2 •4H 2 O. [24][25][26] One way to modify assembly algorithms is with 4′-(4alkyloxyphenyl)-4,2′:6′,4″-terpyridines (Scheme 2) in which the steric demands of the 4′-substituent are altered. We have shown that 1D [Zn 2 (OAc) 4 (4′-(4-ROC 6 H 4 )-4,2′:6′,4″-tpy)] n coordination polymers in which the main packing interactions are π-stacking between arene domains are favoured for small R groups, whereas with longer-chain alkoxy units in which van der Waals interactions are important, discrete complexes [Zn 2 (OAc) 4 (4′-(4-ROC 6 H 4 )-4,2′:6′,4″-tpy) 2 ] form.…”