Single and Double-Stranded 1D-Coordination Polymers with 4′-(4-Alkyloxyphenyl)-3,2′:6′,3″-terpyridines and {Cu2(μ-OAc)4} or {Cu4(μ3-OH)2(μ-OAc)2(μ3-OAc)2(AcO-κO)2} Motifs

Abstract

Five coordination polymers formed from combinations of copper(II) acetate and 4′-(4-alkyloxyphenyl)-3,2′:6′,3″-terpyridines with methoxy (1), n-butoxy (2), n-pentyloxy (3) and n-heptyloxy (4) substituents are reported. Reaction of 1 with Cu(OAc)2∙H2O leads to the 1D-polymer [Cu2(μ-OAc)4(1)]n in which {Cu2(μ-OAc)4} paddle-wheel units are connected by ligands 1, or [{Cu4(μ3-OH)2(μ-OAc)2(μ3-OAc)2(AcO-κO)2(1)2}·2MeOH]n in which centrosymmetric tetranuclear clusters link pairs of ligands 1 to give a double-stranded 1D-polymer. Layering solutions of Cu(OAc)2∙H2O (in MeOH) over 2, 3 or 4 (in CHCl3) leads to the assembly of the 1D-polymers [2{Cu2(μ-OAc)4(2)}·1.25MeOH]n, [Cu2(μ-OAc)4(3)]n and [{Cu2(μ-OAc)4(4)}·0.2CHCl3]n. In all compounds, the 3,2′:6′,3″-tpy unit coordinates only through the outer pyridine rings, but the conformation of the 3,2′:6′,3″-tpy responds to changes in the length of the alkyloxy tails leading to changes in the conformation of the polymer backbone and in the packing of the chains in the crystal lattice in the chains featuring {Cu2(μ-OAc)4} paddle-wheel linkers.

Directing 2D-Coordination Networks: Combined Effects of a Conformationally Flexible 3,2′:6′,3″-Terpyridine and Chain Length Variation in 4′-(4-n-Alkyloxyphenyl) Substituents

“…Figures S2-S6 in the supporting information display the 1 H, 13 C{ 1 H} NMR and solid-state IR spectra of 3, and NMR assignments (see Section 3.2) were made using 2D methods. The solution absorption spectrum of 3 ( Figure 2) is reminiscent of the spectra of other members of the homologous series of ligands shown in Scheme 2 [11,19,20], and the absorptions are assigned to a combination of spin-allowed π*←n and π*←π transitions.…”

“…A well-established route to 4 -aryl functionalized 2,2 :6 ,2"-terpyridines is the one-pot strategy of Wang and Hanan [8], and this methodology has also been used to prepare the 3,2 :6 ,3"-terpyridines 1 [19], 2 [20] and 4-6 [11,20,21]. However, in the case of compound 3, this strategy failed [20] and led instead to the cyclic product 3a (Scheme 3).…”

“…3-Acetylpyridine, 4-hydroxybenzaldehyde and 1-bromopropane were purchased from Acros Organics (Chemie Brunschwig AG, Basel, Switzerland) and were used as received. Ligands 2, 4, 5 and 6 were prepared as previously reported [11,20,21].…”

“…The 3,2 :6 ,3"-tpy and 4,2 :6 ,4"-tpy metal-binding domains differ in their degrees of conformational flexibility [10]. We recently demonstrated that in a series of 1D-coordination polymers [Cu 2 (µ-OAc) 4 (L)] n in which L is a 4 -(4-n-alkyloxyphenyl)-substituted 3,2 :6 ,3"-tpy ligand, conformational changes of the 3,2 :6 ,3"-tpy domain associated with an increase in the length of the n-alkyloxy substituent results in significant changes in the conformation and packing of the coordination polymer chains [11]. The use of 4,2 :6 ,4"-tpy ligands, often functionalized in the 4 -position, as building blocks in coordination polymers and networks has gained in popularity over the last decade [12,13].…”

“…In a continuation of our investigations of the coordination of 4 -(4-alkyloxyphenyl)-3,2 :6 ,3"-tpy ligands [11,19], we now explore the effects of increasing the length of the alkyloxy substituent from methoxy to n hexyloxy (ligands 1-6, Scheme 2).…”