Coordination polymers based on divergent terpyridine ligands

This work describes the design and synthesis of 4,2’:6’,4’’-terpyridine ligands and their use in coordination polymers with various metal salts. In that goal, a series of novel mono- 4,2’:6’,4’’-terpyridines bearing aryl substituents on the 4’ position was prepared. Then, a series of back-to-back 4,2’:6’,4’’-terpyridines, which is a new class of compounds, connected through the same 4’ positions with various rigid spacers were synthesized. First, their synthesis, NMR, UV-VIS, fluorescence and most importantly single crystal X-ray structures are presented and compared. The next section describes the reactions of the mono- 4,2’:6’,4’’-terpyridines with metal acetates (mainly Zn(II)), which yielded various onedimensional coordination polymers. Afterwards the reactions of the same ligands with various Zn(II) halides to produce mostly metalloxexacycles are discussed. Also, a number of host-guest attempts are presented. In the last section, the reactions of the back-to-back 4,2’:6’,4’’-terpyridines with various Zn(II) halides, which resulted in the formation of 2D nets, are displayed and the effect of the spacers was considered

Do perfluoroarenearene and C–HF interactions make a difference to the structures of 4,2′:6′,4′′-terpyridine-based coordination polymers?

The consequences for the structures of coordination polymers of introducing fluoro substituents into the terminal phenyl domain of 4′-(biphenyl-4-yl)-4,2′:6′,4′′-terpyridine (1) have been investigated. Reaction between Cu(OAc)₂·H₂O and 4′-(2′,3′,4′,5′,6′-pentafluorobiphenyl-4-yl)-4,2′:6′,4′′-terpyridine (2) yields the one-dimensional coordination polymer [Cu₂(μ-OAc)₄(2)]n which contains paddle-wheel {Cu₂(OAc)₄} nodes bridged by ligands 2. The compound is isostructural with [Cu₂(μ-OAc)₄(1)]n. When Cu(OAc)₂·H₂O reacts with a 1 : 1 mixture of 1 and 2, [Cu₂(μ-OAc)₄(1)]n and [Cu₂(μ-OAc)₄(2)]n co-crystallize with 1 and 2 disordered over one ligand site; the one-dimensional coordination polymer is isostructural with each of [Cu₂(μ-OAc)₄(1)]n and [Cu₂(μ-OAc)₄(2)]n indicating that replacing H by F substituents in the peripheral arene ring has no effect on the overall solid-state structure: tpy⋯tpy π-stacking is preserved, arene⋯arene πH⋯πH interactions are replaced by perfluoroarene⋯arene πF⋯πH interactions, and H⋯H contacts are replaced by H⋯F interactions. In stark contrast to the latter observations, the reaction of Zn(OAc)₂·2H₂O with perfluoro derivative 2 yields [Zn₅(OAc)₁₀(2)₄·11H₂O]n as the dominant one-dimensional polymer; minor amounts of the anticipated polymer [Zn₂(μ-OAc)₄(2)]n are also formed. The solid-state structure of [Zn₅(OAc)₁₀(2)₄·11H₂O]n consists of quadruple-stranded polymer chains assembled from {Zn₅(2)₄} subchains interconnected by {Zn₅(OAc)₁₀} units. Within each chain, πF⋯πF and πH⋯πH stacking interactions are dominant, while the observed assembly of chains into sheets and π-stacking between arene units in adjacent sheets mimic the dominant interactions in the single-stranded chains observed in [Zn₂(μ-OAc)₄(1)]n, [Zn₂(μ-OAc)₄(2)]n, [Cu₂(μ-OAc)₄(1)]n, [Cu₂(μ-OAc)₄(2)]n and [Cu₂(μ-OAc)₄(1)]n·[Cu₂(μ-OAc)₄(2)]n

Metallohexacycles containing 4′-aryl-4,2′:6′,4′′-terpyridines: conformational preferences and fullerene capture

4′-(4-Biphenylyl)-4,2′:6′,4′′-terpyridine (1) reacts with ZnCl2 or ZnBr2 to produce discrete metallohexacycles instead of the expected one-dimensional coordination polymers. Structural determination of [{ZnCl2(1)}6] and [{ZnBr2(1)}6] reveals that the metallomacrocycles adopt a conformation in which the biphenyl domains are in an alternating up/down arrangement (conformer I). The hexamers pack into tubes; within each tube, biphenyl domains of every second hexamer are interdigitated, and these assemblies then interlock to produce a rigid architecture supported by pyridine–phenyl face-to-face contacts. π-Stacking between 4,2′:6′,4′′-tpy domains operates between adjacent tubes. Reaction of ZnCl2 or ZnBr2 with 4′-(2′,3′,4′,5′,6′-pentafluorobiphenyl-4-yl)-4,2′:6′,4′′-terpyridine (2) leads to [{ZnCl2(2)}6] and [{ZnBr2(2)}6], each crystallizing in two conformations; the centrosymmetric chair-conformer (II) is dominant with respect to the tub-like conformer I. Both conformers pack into tube assemblies, but that consisting of conformer II is less rigid than that of I. Reaction of 4′-(4-(naphthalen-1-yl)phenyl)-4,2′:6′,4′′-terpyridine (3) with ZnCl2 or ZnBr2 leads to [{ZnX2(2)}6] (X = Cl, Br) in conformer I; disordering of the naphthyl substituents is problematic. Assembly of the metallohexacycle in the presence of C60 results in the formation of the host–guest complex [2{ZnCl2(3)}6·C60]·6MeOH·16H2O. The [{ZnCl2(3)}6] units assemble into a tube-like array that mimics that observed in the parent host. In the host–guest complex, each crystallographically-ordered C60 is trapped between six ordered naphthyl units, three from one hexamer and three from its interdigitated partner, and the C60–six-naphthyl unit sits centrally within a second [{ZnCl2(3)}6] macrocycle. In contrast to previously described tube-like host–guest assemblies featuring fullerene entrapment, [2{ZnCl2(3)}6·C60] is unusual in having an ordered array of C60 molecules present in every other available cavity, despite the fact that sterically, the ‘empty’ cavity could, in principle, host a C60 guest

Cobalt(II) coordination polymers with 4 '-substituted 4,2 ':6 ',4 ''- and 3,2 ':6 ',3 ''-terpyridines : engineering a switch from planar to undulating chains and sheets

Two new ligands 4`-(1H-imidazol-4-yl)-4,2`:6`,4 ``-terpyridine (3) and 4`-(4-dimethylaminophenyl)-3,2`:6`,3 ``-terpyridine (4) are described. Structure determination of 3 center dot CHCl3 reveals the assembly of hydrogen-bonded chains of molecules of 3; the preference for NHimidazole center dot center dot center dot N-tpy over NHimidazole center dot center dot center dot N-imidazole hydrogen bonds is consistent with the relative basicities of the heterocyclic rings. Reactions of Co(NCS)(2) with 4`-phenyl-4,2`:6`,4 ``-terpyridine (1), 4`-(4-ethynylphenyl)-4,2`:6`,4 ``-terpyridine (2) or 3, produce two-dimensional networks. In each, the Co2+ ion is in an octahedral trans-Co(N-tpy)(4)(NCS)(2) environment. [2Co(1)(2)(NCS)(2)center dot 5H(2)O(n)] and [Co(3)(2)(SCN)(2)center dot 2MeOH(n)] exhibit (4,4) nets. In [Co(2)(2)(NCS)(2)center dot 0.67C(2)H(4)Cl(2)center dot MeOH center dot H2O(n)], a (6,3) net is present. In all three coordination networks, there is substantial twisting of the 4,2`:6`,4 ``-terpyridine backbone and as a consequence, the dominant packing interactions are not the face-to-face pi-stacking of tpy domains that are ubiquitous in many solid-state structures containing metal-bound tpy domains. As a preliminary investigation of the effects of altering the directionality of the donor set in the terpyridine domain, Co(SCN)(2) was reacted with ligand 4, and the one-dimensional coordination polymer [Co(4)(MeOH)(2)(NCS)(2)(n)] was isolated. Ligand 4 adopts a trans, trans-arrangement and the zig-zag chains are undulating. The buckled sheets that result from the intermeshing of the chains contrast with the planar sheets observed in [Cd(5)(OH2)(2)(ONO2)(O2NO)center dot H2O(n)] (5 = 4`-(4-dimethylaminophenyl)-4,2`:6`,4 ``-terpyridine). The observed packing interactions suggest that the change from planar to undulating chains and sheets on going from 5 to 4 is a consequence of optimizing face-to-face pi-stacking interactions