A High‐Conductivity Crystal Containing a Copper(I) Coordination Polymer Bridged by the Organic Acceptor TANC

Abstract

Artificial conductors constructed from molecular building blocks can replicate unique low-dimensional electron-transport phenomena depending on the nature of their molecular components.[1] For example, Cu(DCNQI) 2 (DCNQI = N,N'-dicyanoquinodiimine) systems formed from coordination polymers containing alternating 3D linkages between Cu ion donors and organic DCNQI acceptors exhibit an interesting metal-insulator (M-I) transition under high pressure. This behavior is due to the interaction between the localized 3d-electron bands of the Cu ions and the p-electron conductive bands of DCNQI.[2] Therefore, the appropriate combination of donors and acceptors as molecular building blocks, which often form an electron-conducting solid, plays an important role in determining the electron-transport character of a molecular crystal.Molecules that form high-conductivity molecular solids, particularly organic acceptors, have been limited thus far to cyanoquinoid derivatives such as TCNQ [3] and DCNQI [4] and the metal complex [M(dmit) 2 ] (dmit = 1,3-dithiole-2-thioxo-4,5-dithiolato).[5] Molecular conductors with various electrondonor frameworks based on heterocyclic structures containing a chalcogen atom such as tetrathiafulvalene (TTF) [6] and tetramethyltetraselenofulvalene (TMTSF) [7] have also been realized, and studies are underway to discover a fundamental molecule with a stable electron-accepting framework to form molecular conductors with a desired transport behavior. Herein, we report a modifiable electron acceptor with 5,6,11,12-tetraazanaphthacene (TANC) as a new fundamental framework and the preparation of a high-conductivity crystal (1) from Cu I -TANC coordination polymers.TANC was prepared by modifying a synthetic procedure first reported by Hill.[8] The yellow precipitate obtained from the thermal condensation between o-phenylenediamine and oxamide contains 2,2'-bibenzimidazole and 5,11-dihydro-5,6,11,12-tetraazanaphthacene (FFV) in a 3:1 ratio. This mixture was oxidized with PbO 2 in MeCN to give brown crystals of TANC in 20 % yield. The cyclic voltammogram of TANC in MeCN exhibits two reversible one-step, oneelectron waves in the reverse sweep (E 1 1/2 = À0.20 and E 2 1/2 = À0.88 V vs Ag/AgCl), which means that TANC is a weaker electron acceptor than organic acceptors such as TCNQ and DCNQI that form high-conductivity materials. [9] Unfortunately, TANC cannot be employed as an organic semiconductor with n-type characteristics.The TANC radical anion can be isolated from an electron disproportionate reaction between FFV and TANC under basic conditions. This compound was obtained as a green precipitate under anaerobic conditions, which immediately turns gray upon exposure to air. The ESR spectrum of the precipitate exhibits a typical anisotropic peak (g ? = 2.011 and g k = 2.0091) that stabilizes at room temperature (see the Supporting Information).The high-conductivity crystal 1, which has the composition [{Cu(TANC)}F 0.5 ] n , was obtained from the reaction between TANC and [Cu(MeCN) 4 ]BF 4 in MeOH/MeCN in t...

Dipole‐Driven Self‐Organization of Liquid‐Crystalline N‐Heteroacene Derivatives Showing Redox‐Properties

“…N ‐Heteroacenes, which consist of electron‐deficient imino‐ N atoms in linearly π‐conjugated polycyclic oligoacene framework, are well‐known as electron acceptor and n ‐type organic semiconductors . We have previously reported 5,6,11,12‐tetraazanaphtacene (TANC)‐based liquid‐crystalline (LC) materials, field‐effect transistor in thin films, and Cu‐coordinated molecules in single crystal ,. Among them, LC TANC derivatives self‐organized various superstructures such as 1D columnar LC and 2D layered smectic LC phases through various interactions such as π‐π interaction, hydrophobic interaction, and nanosegregation .…”

Interface Structures and Electronic States of Epitaxial Tetraazanaphthacene on Single-Crystal Pentacene

“…No matter how promising the characteristics of pentacene are, they are not sufficient for realizing practical p–n junction devices such as solar cells because pentacene, and other unsubstituted acenes such as naphthacene (tetracene), are mostly p-type (donor) materials and it is not easy to switch the polarity of these molecules. To make favorable pairs with these p-type aromatic hydrocarbons, a number of complementary n-type (acceptor) compounds have been synthesized by the introduction of elements of higher electronegativities such as halogens and nitrogen to their backbones [ 7 , 8 , 9 , 10 , 11 ]. In particular, molecules with nitrogen-containing heterocycles are attracting recent interest as non-fullerene acceptor molecules for the application of organic solar cells and as high mobility n-type organic semiconductors [ 12 ].…”

Synthesis, Crystal Structure, and Electroconducting Properties of a 1D Mixed-Valence Cu(I)–Cu(II) Coordination Polymer with a Dicyclohexyl Dithiocarbamate Ligand

“…Crystal engineering of coordination polymers attracts increased attention in the field of materials science because of their exceptional chemical and physical properties, such as magnetic [1][2][3] and conductive [4][5][6][7][8][9][10][11][12][13][14][15][16][17], dielectric [18][19][20], gas-absorbing [21][22][23], and catalytic properties [24][25][26][27]. In particular, mixed-valence coordination polymers have attracted considerable interest as a new class of functional materials because of their unique infinite structures and electronic states formed by the combination of different metal ions having versatile coordination architectures and a variety of organic bridging ligands.…”