Highly Oxidized Semiconducting Coordination Polymers – Coupled Oxidation and Coordination of Guanidine Electron Donors

Abstract

Redox and coordination processes are coupled in the course of reactions of the organic electron donors 1,2,4,5‐tetrakis(tetramethylguanidino)benzene (1) and 1,2,4,5‐tetrakis(N,N′‐dimethyl‐N,N′‐ethyleneguanidino)benzene (2) with silver salts. Experiments with several different silver salts show that the product structure is significantly affected by the properties of the anion in these salts. Chain polymers are the products of reactions with AgPF6 or AgBF4, in which dicationic organic building blocks are connected by silver ions. Experiments with AgNO3 yielded either dinuclear complexes (with 1) or 2D networks (with 2). If the salt Ag[Al{OC(CF3)3}4], featuring a weakly coordinating anion, was used, simple silver‐free salts of the guanidine dication were obtained. The thermal stability, optical properties, and electrical conductivity were studied in detail for the product polymer {[(1)Ag](PF6)3}n. From the temperature dependence of the electric conductivity, this compound was found to be a semiconductor with a band gap of approximately 3 eV. The experiments were complemented by quantum chemical calculations at density‐functional‐theory level on the band structure of this and a related polymer. The electronic situation was further analyzed with the aid of molecular model complexes, which were either synthesized or calculated.

Guanidinyl‐Functionalized Aromatic Compounds (GFAs) – Charge and Spin Density Studies as Starting Points for the Development of a New Class of Redox‐active Ligands

“…As expected, such complexes are examples of the typ [Ag I | GFA 2+ | Ag I ]; hence not the metal but the ligand is oxidized. We indeed found examples for this type (see the two complexes [ttmgb{Ag(pico) 2 } 2 ] and [ttmgb{Ag(NO 3 ) 2 } 2 ]51 in Figure 10).…”

“…An example for a one step synthesis is the reaction between ttmgb and AgPF 6 , leading to the one‐dimensional coordination polymer {[Ag(ttmgb)](PF 6 ) 3 } n (see Figure 11). 51 It features cationic chains, in which silver ions connect the twofold oxidized guanidine ligands. The PF 6 – anions surround the chains.…”

“…Right: Density of states plot for the coordination polymer {[(CuI) 2 (ttmgb)](I 3 ) 2 } n . See references45,51.…”

Electropolymerization of N,N'-Diphenylguanidine in Non-Aqueous Aprotic Solvents and Alcohols

“…They can bind readily to metal cations and form complexes having different properties and therefore they proved themselves to be appropriate in many applications. Guanidine benzene derivatives can build up Ag + bridged multicore metal complexes which have semiconducting properties [12] and metal ion bridged polymers also form with silver dicyanamide [13]. Their color changes remarkably by the degree of protonation and due to electrochemical reactions [14][15][16].…”

Bisguanidines with Biphenyl, Binaphthyl, and Bipyridyl Cores: Proton‐Sponge Properties and Coordination Chemistry

“…[18] In metal complexes, ttmgb was either a neutral, radical monocationic, or dicationic ligand. [14,[19][20][21][22] For comparison, most of the commonly used redox-active ligands (e.g., o-quinone or a-diimine ligands) are neutral-anionic. [23] The observation of temperature-dependent electrical conductivity in the coordination polymer {[(CuI) 2 -A C H T U N G T R E N N U N G (ttmgb)](I 3 ) 2 } n [24] (in line with a classical semiconductor) was interpreted as a proof of principle for the possibility of metal-ligand charge flow, which is typical for "noninnocent" ligand behaviour.…”