Hydrogen-Bonded Networks in Organic Conductors:  Crystal Structures and Electronic Properties of Charge-Transfer Salts of Tetracyanoquinodimethane with 4,4‘-Biimidazolium Having Multiprotonated States

Abstract

[structure: see text] Novel hydrogen-bonded charge-transfer salts of TCNQ with mono- and diprotonated 4,4'-biimidazolium were synthesized in order to demonstrate the high potential of the 4,4'-biimidazole system in a molecular conductor from the viewpoint of crystal engineering and electronic modulation. Crystal structure analyses of neutral 4,4'-biimidazole and TCNQ salts revealed the formation of two types of hydrogen-bonding modes of the 4,4'-biimidazole moiety depending on the protonated states. Neutral 4,4'-biimidazole possessed a linear chain mode of hydrogen-bonding to construct two-dimensional network. In the TCNQ salt of monoprotonated 4,4'-biimidazolium, the 4,4'-biimidazole moiety formed a dimer by a complementary mode of hydrogen-bonding. In contrast, the salt of diprotonated 4,4'-biimidazolium showed a double linear chain mode of hydrogen-bonding to construct a three-dimensional network. The formation of two types of hydrogen-bonding modes made the difference in the stacking patterns of TCNQ columns and in their transport properties. The TCNQ salt of diprotonated 4,4'-biimidazolium exhibited high electrical conductivity (sigma(rt) = 1.1 x 10(-1) S cm(-1)).

Hydrogen-bonded assembly and binding affinity of the multi-point acceptor and isophthalic acid

“…As the water molecule was put into the cavum of complex 1 to form complex 9, the lengths of the hydrogen bonds were elongated. The distances between H(33) and O(42), H(48) and N(22), H (25) and O(45), and H(46) and N(1) were 0.2390, 0.2440, 0.2190 and 0.2440 nm, basically agreeable with the XRD experimental results in organic conductors determined by Morita et al [28]. It was illustrated that the cavum of complex 1 was enlarged in order to contain small molecules.…”

Assembling Extended Structures with Flavonoids

“…Flavanone 3 was also mixed with DABCO in a 1:1 ratio in THF. Slow evaporation of this solution led to the crystallization of material [3][4] in P2 1 /n and reveals three-centered hydrogenbonding interactions ( Figure 6). The 7-hydroxyl moiety of each flavanone has been deprotonated by a DABCO molecule and has two hydrogen bonding contacts: one from the 4′-hydroxyl moiety of another flavanone (O4 · · · O5 2.5915(19) Å); the other from the protonated nitrogen atom of an HDABCO + (N1 · · · O5 2.579(2) Å).…”

“…Discrete 3-D layers are then formed as adjacent 2-D layers are interconnected by additional hydrogen bonding interactions with additional DABCO molecules (O14 · · · N61 2.646(9) Å, O13 · · · N61 3.145(11) Å). A section of one 3-D layer is displayed down the a axis in Figure 9 and down the c axis in [3][4] revealing π-π stacking. Some hydrogen atoms have been omitted for clarity.…”

“…Separate solutions of 4′,5,7-trihydroxyflavanone (3) (0.270 g, 1.00 mmol) and DABCO (4) (0.112 g, 1.00 mmol) were prepared in enough THF for full dissolution. After the two solutions were mixed and allowed to stand, yellow crystals of [3][4] formed within one day. The Laue symmetry and systematic absences were consistent with the monoclinic space group P2 1/n.…”

Probing physical properties at the nanoscale using atomic force microscopy

“…In this regard, other relatively simple polycarboxylic acids may fulfill a similar function and studies exploring this possibility are underway. Alternatively, 1 may also contribute in some degree to the conducting properties of these assemblies as a consequence of intermolecular arene edge-to-face interactions and/or participation in extended H-bonded networks 115,116. The synthetic accessibility of additional tetraarylethylene and bis(pyridine) derivatives should facilitate formulation of systematic structure-activity studies designed to shed light on this issue.In conclusion, we have successfully prepared and characterized a series of stable crystals from acetic acid-substituted tetraphenylethylene and three bis(pyridine)s. Two of these supramolecular assemblies were found to exhibit conductivities comparable to those of established organic semiconductors as determined through CP-AFM.Importantly, the conducting properties of these multi-component crystals can be modulated as a function of bis(pyridine) partner, opening exciting opportunities for construction of new tunable electro-active organic materials.…”