A complementary organic inverter of porphyrazine thin films: low-voltage operation using ionic liquid gate dielectrics

Molecular Structure, Thermodynamic and Spectral Characteristics of Metal-Free and Nickel Complex of Tetrakis(1,2,5-thiadiazolo)porphyrazine

The Knudsen effusion method with mass spectrometric control of the vapor composition was used to study the possibility of a congruent transition to the gas phase and to estimate the enthalpy of sublimation of metal-free tetrakis(1,2,5-thiadiazolo)porphyrazine and its nickel complex (H₂TTDPz and NiTTDPz, respectively). The geometrical and electronic structure of H₂TTDPz and NiTTDPz in ground and low-lying excited electronic states were determined by DFT calculations. The electronic structure of NiTTDPz was studied by the complete active space (CASSCF) method, following accounting dynamic correlation by multiconfigurational quasi-degenerate second-order perturbation theory (MCQDPT2). A geometrical structure of D_2h and D_4h symmetry was obtained for H₂TTDPz and NiTTDPz, respectively. According to data obtained by the MCQDPT2 method, the nickel complex possesses the ground state ¹A_1g, and the wave function of the ground state has the form of a single determinant. Electronic absorption and vibrational (IR and resonance Raman) spectra of H₂TTDPz and NiTTDPz were studied experimentally and simulated theoretically.

Peculiarities of electronic structure and chemical bonding in iron and cobalt metal complexes of porphyrazine and tetra(1,2,5-thiadiazole)porphyrazine

The geometrical and electronic structures of iron and cobalt metal complexes of porphyrazine and tetra(1,2,5-thiadiazole)porphyrazine in ground and low-lying excited electronic states were determined by DFT calculations and the complete active space (CASSCF) method with following accounting dynamic correlation by multiconfigurational quasidegenerate second-order perturbation theory (MCQDPT2). A geometrical structure of D[Formula: see text] symmetry has been obtained for all four complexes. According to data obtained by the MCQDPT2 method, the complexes of cobalt and iron possess the ground states 2A[Formula: see text] and 3A[Formula: see text], respectively, and wave functions of the ground states have the form of a single determinant. It is shown that the crystal field theory (CFT) can be used to describe the sequence of electronic states of the investigated complexes. The nature of the bonds between metal atoms and nitrogen atoms has been described using the analysis of the electron density distribution in the frame of Bader’s quantum theory of atoms in molecule (QTAIM).

Chemical potentials of electric double layers at metal-electrolyte interfaces: dependence on electrolyte concentration and electrode materials, and application to field-effect transistors

When a metal is soaked in an electrolyte solution, the metal and solution affect each other through the formation of electric double layers (EDLs) at their interfaces. The EDLs at metal-electrolyte interfaces can realize high-density charge-carrier injections and accumulations, and thus have recently attracted attention for their potential application to energy storage, and electronic and electrochemical devices. In such EDL-based devices, including field-effect transistors (FETs), the potential energy of surface electrons in the metal electrodes (EM) governs the transistor device performance. This is in clear contrast to redox-driven electrochemical devices such as dye-sensitized solar cells and electrochromic devices, whose performance is primarily governed by the potentials of the redox-active species. However, there has been no systematic research to bridge the distance between metal electrons and electrolyte ions. In the present study, we carefully examined the dependence of EM of ITO, Au and Pt electrodes on the concentration of the PEG solutions of LiCl and MgCl2, because it has been well established that the chemical potential of electrolyte solutions is dependent on the solution concentrations. Our results showed that, at the same electrolyte concentration, the values of EM increased in the order of ITO, Au and Pt; moreover, on the same electrode, EM showed linear decreases as a function of the logarithm of the electrolyte concentrations. To understand these behaviors, we developed a theoretical treatment of the EDLs based on the simple Gouy-Chapman model, and obtained the theoretical expressions of EM in terms of the concentration of electrolyte and the work function of the metal electrode (ΦM), which were found to successfully explain the dependences of EM on the electrolyte concentration and the electrode materials. We also examined the EDL-FETs of platinum phthalocyanine (PtPc), with various LiCl-PEG solutions of different concentrations as gate electrolytes. The threshold voltage eVT and EM exhibited a linear relation, which was well explained by the relation between EM and the valence band energy EVB of PtPc. The transfer characteristics at various gate voltage VG were found to be well normalized by a function of eVG + EM.

DFT Study of Molecular and Electronic Structure of Ca(II) and Zn(II) Complexes with Porphyrazine and tetrakis(1,2,5-thiadiazole)porphyrazine

Electronic and geometric structures of Ca(II) and Zn(II) complexes with porphyrazine (Pz) and tetrakis(1,2,5-thiadiazole)porphyrazine (TTDPz) were investigated by density functional theory (DFT) calculations and compared. The perimeter of the coordination cavity was found to be practically independent on the nature of a metal and a ligand. According to the results of the natural bond orbital (NBO) analysis and quantum theory of atoms in molecules (QTAIM) calculations, Ca-N bonds possess larger ionic contributions as compared to Zn-N. The model electronic absorption spectra obtained with the use of time-dependent density functional theory (TDDFT) calculations indicate a strong bathochromic shift (~70 nm) of the Q-band with a change of Pz ligand by TTDPz for both Ca and Zn complexes. Additionally, CaTTDPz was synthesized and its electronic absorption spectrum was recorded in pyridine and acetone.

Tetrakis(1,2,5-thiadiazolo)porphyrazines. 9. Synthesis and spectral and theoretical studies of the lithium(i) complex and its unusual behaviour in aprotic solvents in the presence of acids

The template cyclotetramerization of 1,2,5-thiadiazolo-3,4-dicarbonitrile in the presence of lithium n-butoxide in n-butanol leads to the Li(i) complex of tetrakis(1,2,5-thiadiazolo)porphyrazine. Various possible structures of dilithium and monolithium complexes have been considered by DFT/B3LYP molecular modelling using the cc-pvtz basis set, and their theoretical IR and UV-VIS spectra have been calculated. The experimental ⁷Li NMR, IR and UV-VIS spectra measurements show that the complex contains two inequivalent lithium atoms - one is coordinated to the macrocyclic dianion to form the anionic lithate complex [TTDPaLi]^-, while the other forms the solvated countercation [Li(Solv)₄]⁺. The lithate complex is stable in protic solvents, such as methanol, and is soluble in water to give aggregated solutions. Its demetallation occurs in the presence of acids (CH₃COOH, CF₃COOH, H₂SO₄). In aprotic solvents (DMF, DMSO), the acid-catalyzed formation of the [TTDPa]^2- dianion is observed which is followed by the formation of the meso-protonated form {H[TTDPa]}^- at higher acid concentrations. Both processes can be reversed by the addition of a lithium salt excess or neutralization of the acid. The fluorescence quantum yield for the lithate complex [TTDPaLi]^- is much higher than that for the [TTDPa]^2- dianion (0.34 and 0.01 in DMSO), and this can be used for detecting low concentrations of acids and Li⁺ in aprotic solvents (10^-6-10^-5 M). The first reversible reduction of the macrocycle in the anionic lithate complex (-0.94 V vs. SCE in DMSO) is ∼0.5 V more difficult than that in the complexes with divalent metals [TTDPaM] (M = Mg^II, Zn^II, Cu^II).

Microscopic properties of ionic liquid/organic semiconductor interfaces revealed by molecular dynamics simulations

Structural and dynamic properties of an ionic liquid are compared on several organic semiconductors.

Preparation, optical and electrochemical properties, and molecular orbital calculations of tetraazaporphyrinato ruthenium (II) bis(4-methylpyridine) fused with one to four diphenylthiophene units

2,5-Diphenyl-3,4-dicyanothiophene (1) and phthalonitrile (2) were mixed and treated with ruthenium (III) trichloride, 4-methylpyridine, and 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) in 2-ethoxyethanol at 135°C, to produce low-symmetrical tetraazaporphyrins (TAPs) (3), (4), (5), and (6) with one to three thiophene rings. Two thiophene-annelated tetraazaporphyrins were isolated as opposite and adjacent isomers 4 and 5. The structure of 3 was determined by X-ray crystallography, showing that the thiophene ring linked at the 3,4-positions on the tetraazaporphyrin scaffold deviates from the mean plane of the four central pyrrole nitrogen atoms (N1-N3-N5-N7). Optical and electrochemical properties of the products were examined by UV-vis and magnetic circular dichroism (MCD) spectroscopy, together with cyclic voltammetry. In the (1)H NMR spectra, the signals of 4-methylpyridine coordinating to the central ruthenium atom appeared at a higher magnetic field than those of uncoordinated 4-methylpyridine itself due to the shielding effect of the TAP ring. Increasing the number of fused thiophene rings resulted in 1) lower magnetic field shifts of the signals of axially coordinated 4-methylpyridine in the (1)H NMR spectra, 2) lower energy shifts of the Q band absorption in the UV-vis spectra, and 3) decreasing (cathodic shift) of the first oxidation potentials. The structures of simplified model compounds were optimized using the DFT method with the Gaussian 09 program at the B3LYP/LANL2DZ level for the Ru atom and the B3LYP/6-31G (d, p) level for the C, H, N, and S atoms. The optimized structures were utilized to calculate the NMR shielding constants, the HOMO and LUMO orbital energies, and the electronic absorption spectra.

The optical characterization of metal-mediated aggregation behaviour of amphiphilic Zn(ii) phthalocyanines

Addition of Ag⁺ cations induces J-aggregation in ultrathin films of both symmetrically and asymmetrically substituted Zn(ii) phthalocyanines.

n-Type small aromatic core diimides flanked with electron donating thienylethyl moieties and electrical responses in organic devices

Synthesis and electrical characteristics of two new n-type small aromatic core diimide derivatives functionalized with an electron donating moiety are reported.

Electric-double-layer field-effect transistors with ionic liquids

Charge carrier control is a key issue in the development of electronic functions of semiconductive materials. Beyond the simple enhancement of conductivity, high charge carrier accumulation can realize various phenomena, such as chemical reaction, phase transition, magnetic ordering, and superconductivity. Electric double layers (EDLs), formed at solid-electrolyte interfaces, induce extremely large electric fields. This results in a high charge carrier accumulation in the solid, much more effectively than solid dielectric materials. In the present review, we describe recent developments in the field-effect transistors (FETs) with gate dielectrics of ionic liquids, which have attracted much attention due to their wide electrochemical windows, low vapor pressures, and high chemical and physical stability. We explain the capacitance effects of ionic liquids, and describe the various combinations of ionic liquids and organic and inorganic semiconductors that are used to achieve such effects as high transistor performance, insulator-metal transitions, superconductivity, and ferromagnetism, in addition to the applications of the ionic-liquid EDL-FETs in logic devices. We discuss the factors controlling the mobility and threshold voltage in these types of FETs, and show the ionic liquid dependence of the transistor performance.

First tellurium-containing phthalocyanine analogues: strong effect of tellurium on spectral, redox and conductivity properties of porphyrazines with annulated chalcogenodiazole ring(s)

The first tellurium-containing phthalocyanine analogues have been prepared and spectroscopically characterised: the Mg(II) complex of tetra(1,2,5-telluradiazolo)porphyrazine and a low-symmetry tert-butyl substituted Mg(II) tribenzoporphyrazine with one fused 1,2,5-telluradiazole ring. It was observed that the introduction of Te atom(s) reduces the energy of the Q-transition, facilitates the reduction of the macrocycle and strongly increases the conductivity of thin films.

Tetrachlorinated tetraazaperopyrenes (TAPPs): highly fluorescent dyes and semiconductors for air-stable organic n-channel transistors and complementary circuits

A range of 2,9-perfluoroalkyl-substituted tetraazaperopyrene (TAPP) derivatives (1-5) was synthesised by reacting 4,9-diamino-3,10-perylenequinone diimine (DPDI) with the corresponding carboxylic acid chloride or anhydride in the presence of a base. The reaction of compounds 1-4 with dichloroisocyanuric acid (DIC) in concentrated sulphuric acid resulted in the fourfold substitution of the tetraazaperopyrene core, yielding the 2,9-bisperfluoroalkyl-4,7,11,14-tetrachloro-1,3,8,10-tetraazaperopyrenes 6-9, respectively. The optical and electrochemical data demonstrate the drastic influence of the core substitution on the properties. All compounds are highly luminescent (fluorescence quantum yields of up to Φ=0.8). The LUMO energies of the tetrachlorinated TAPP derivatives (determined by cyclic voltammetry and computed by DFT calulations) were found to be below -4 eV. In the course of this work the performance of TAPP derivatives in organic thin-film transistors (TFTs) was investigated, and their n-channel characteristics with field-effect mobilities of up to 0.14 cm(2)  V(-1)  s(-1) and an on/off current ratio of >10(6) were confirmed. Long-term stabilities of 3-4 months under ambient conditions of the devices were established. Complementary inverters and ring oscillators with n-channel TFTs based on compound 8 and p-channel TFTs based on dinaphtho-[2,3-b:2',3'-f]thieno[3,2-b]thiophene (DNTT) were fabricated on a glass substrate.

Crystal structure, spin polarization, solid-state electrochemistry, and high n-type carrier mobility of a paramagnetic semiconductor: vanadyl tetrakis(thiadiazole)porphyrazine

We report the synthesis, crystal structure, and magnetic, electrochemical, and carrier-transport properties of vanadyl tetrakis(thiadiazole)porphyrazine (abbreviated as VOTTDPz) with S = ½. X-ray crystal analysis reveals two polymorphs, the α and β forms; the former consists of a 1D regular π stacking, while the latter forms a 2D π network. Molecular orbital calculations suggest a V(4+)(d(1)) ground state and a characteristic spin polarization on the whole molecular skeleton. The temperature dependence of the paramagnetic susceptibility of the α form clearly indicates a ferromagnetic interaction with a positive Weiss constant of θ = 2.4 K, which is well-explained by McConnell's type I mechanism. VOTTDPz forms amorphous thin films with a flat and smooth surface, and their cyclic voltammogram curves indicate a one-electron reduction process, which is highly electrochromic, because of a reduction of the porphyrazine π ring. Thin-film field-effect transistors of VOTTDPz with ionic-liquid gate dielectrics exhibit n-type performance, with a high mobility of μ = 2.8 × 10(-2) cm(2) V(-1) s(-1) and an on/off ratio of 10(4), even though the thin films are amorphous.