New Cu^I₂(TCNQ^–II) and Cu^I₂(F₄TCNQ^–II) Coordination Polymers

Abstract

Coordination polymer strips of composition …Cu + 2 .lig 2-.Cu + 2 .lig 2-.Cu + 2 .lig 2-… (where lig 2-= TCNQ 2-or its 2,3,4,5-tetrafluoro analogue) are observed with a wide range of co-ligands (monodentate, bidentate and tridentate). Interdigitation of "thin", planar N-heteroaromatic co-ligands on one strip with those on a neighbor is a common structural feature. Co-ligands too bulky to allow interdigitation give either non-interdigitating strips or 2D sheet structures. Both strips and sheets have 2-connecting Cu centers and 4-connecting tetracynano ligands. As a consequence of the great flexibility of the Cu/tetracyano ligand association, the geometries of the sheet structures vary widely from almost coplanar to highly corrugated and convoluted, in spite of which the same topology is present in all.*Corresponding authors: Fax: +61 9347 5180; Phone +61 3 8344 0341 (BFA),+61 3 8344 6469 (RR) AbstractCoordination polymer strips of composition …Cu + 2 .lig 2-.Cu + 2 .lig 2-.Cu + 2 .lig 2-… (where lig 2-= TCNQ 2-or its 2,3,4,5-tetrafluoro analogue) are observed with a wide range of co-ligands (monodentate, bidentate and tridentate). Interdigitation of "thin", planar N-heteroaromatic co-ligands on one strip with those on a neighbor is a common structural feature. Co-ligands too bulky to allow interdigitation give either noninterdigitating strips or 2D sheet structures. Both strips and sheets have 2-connecting Cu centers and 4-connecting tetracynano ligands. As a consequence of the great flexibility of the Cu/tetracyano ligand association, the geometries of the sheet structures vary widely from almost coplanar to highly corrugated and convoluted, in spite of which the same topology is present in all.

Multifunctional Coordination Polymer Exhibiting Reversible Mechanical Motion Allowing Selective Uptake of Guests and Leading to Enhanced Electrical Conductivity

“…Of particular importance are the ν­(CN) bands, which provide a useful indication of the oxidation state of the F 4 TCNQ moiety. The ν­(CN) frequencies observed for the solvated open form, the desolvated closed form, and the adducts with nitrobenzene, maleic anhydride, benzoquinone, and iodine are remarkably invariant (2198 ± 2, 2153 ± 1, and 2128 ± 2 cm –1 ) and consistent with other examples involving coordinated F 4 TCNQ 2– …”

“…The ν(CN) frequencies observed for the solvated open form, the desolvated closed form, and the adducts with nitrobenzene, maleic anhydride, benzoquinone, and iodine are remarkably invariant (2198 ± 2, 2153 ± 1, and 2128 ± 2 cm −1 ) and consistent with other examples involving coordinated F 4 TCNQ 2− . 28 As can be seen in Figure 6, the vis−NIR spectra of Mn(F 4 TCNQ)(py) 2 , in both the open and closed forms, show little absorption in the observed 5000−25000 cm −1 range, whereas the adducts with electron-accepting guests show significantly enhanced absorption, which is attributed to charge-transfer interactions between the donor F 4 TCNQ 2− components of the framework and the acceptor intercalants.…”

“…More recent work has indicated that this aromatic dianion as well as its tetrafluorinated analogue, 7,7,8,8-tetracyano-2,3,5,6-tetrafluoroquinodimethane (F 4 TCNQ II– , III , X = F) may be stabilized through charge-transfer interactions with electron acceptors or through coordination to metal centers within coordination networks, where it may be generated by deprotonation of its acid form, X 4 TCNQH 2 ( IV , X = H or F). The deprotonation of IV in the presence of metal ions is an approach used to create more than 100 network materials involving X 4 TCNQ II– . − Crystals of coordination polymers incorporating these dianions are typically pale unless they have the opportunity to participate in charge-transfer interactions with electron-deficient species, in which case the crystals can be intensely colored. It is important to emphasize that, whereas the neutral forms of X 4 TCNQ are electron-deficient, allowing it to serve as an acceptor in charge-transfer interactions, the X 4 TCNQ II– form is electron-rich and therefore can act as a donor.…”

Use of the TCNQF42− Dianion in the Spontaneous Redox Formation of [FeIII(L−)2][TCNQF4⋅−]

“…At these very negative potentials, TCNQF 4 . − has been reduced to TCNQF 4 2− , which itself is an excellent ligand . Presumably, coordination and displacement of the nitroxide (L − ) or rearrangement to a bidentate or monodentate form occurs, leaving a new form of ligand that can be further reduced.…”

Untitled

“…At these very negative potentials, TCNQF 4 C À has been reduced to TCNQF 4 2À ,w hich itself is an excellent ligand. [41,42] Presumably,c oordinationa nd displacement of the nitroxide (L À ) or rearrangement to ab identate or monodentate form occurs, leaving an ew form of ligand that can be further reduced. Reductiont oF e I and an internal electront ransfer reactiona lso may occur and square schemes analogous to reactionIIc ould be operative.…”