Inorganic Chemistry, Vol.54, No.4, 1518-1527, 2015
Fully Electron-Transferred Donor/Acceptor Layered Frameworks with TCNQ(2-)
In a series of two-dimensional layered frameworks constructed by two electron-donor (D) and one electron-acceptor (A) units (a D(2)A framework), two-electron transferred systems with D(2)(+)A(2) were first synthesized as [{Ru-2(R-PhCO2)(4)}(2)(TCNQR(x))].(n)(solv) (R = o-CF3, R-x = H-2 (1 ), R = o-CF3, R-x = Me-2 (2 ), R = o-CF3, R-x = F-4 (3 ), R = o-Me, TCNQR(x) = BTDA-TCNQ (4 ), R = p-Me, TCNQR(x) = BTDA-TCNQ (5 ), where TCNQ is 7,7,8,8-tetracyano-p-quinodimethane and BTDA-TCNQ is bis[1,2,5]dithiazolotetracyanoquinodimethane). The D(2)(+)A(2) system was synthesized by assembling D/A combinations of paddlewheel-type [Ru-2(II,II)(R-PhCO2)(4)] complexes and TCNQR(x) that possibly caused a large gap between the HOMO of D and the LUMO of A (Delta EH-L(DA)). All compounds were paramagnetic because of quasi-isolated [Ru2(II,III)](+) units with weakly antiferromagnetically coupled S = 3/2 spins via diamagnetic TCNQR(x)(2) and/or through the interlayer space. The ionic states of these compounds were determined using the HOMO/LUMO energies and redox potentials of the D and A components in the ionization diagram for Delta EH-L(DA) vs Delta E-1/2(DA) (= E-1/2(D) E-1/2(A); E-1/2 = first redox potential) as well as by previously reported data for the D2A and DA series of [Ru-2]/TCNQ, DCNQI materials. The boundary between the one-electron and the two-electron transferred ionic regimes (1e-I and 2e-I, respectively) was not characterized. Therefore, another diagram for Delta EH-L(DA) vs Delta E-1/2(A) E-1(1/2)(A)|, where E-2(1/2)(A) and E-1(1/2)(A) are the second and first redox potentials of TCNQR(x), respectively, was used because the 2e-I regime is dependent on on-site Coulomb repulsion (U = |E-2(1/2)(A) E-1(1/2)(A)|) of TCNQR(x). This explained the oxidation states of 15 and the relationship between Delta EH-L(DA) and U and allowed us to determine whether the ionic regime was 1e-I or 2e-I. These diagrams confirm that a charge-oriented choice of building units is possible even when designing covalently bonded D2A framework systems.