Tetracyanoquinodimethane Derivatives Research Articles

Self-assembled tetracyanoquinodimethane derivatives: differential fluorescent responses on sensing copper and mercury ions in an aqueous medium

TCNQ derivatives/fluorophores, utilized for metal ion sensing, especially Cu2+ and Hg2+ in aqueous medium. Single step, quick synthesis and easy purification highlights their real-time applicability.

Non-Covalent Interactions in Weak Donor–Acceptor Systems Based on Toluene and Tetracyanoquinodimethane Derivatives

Non-Covalent Interactions in Weak Donor–Acceptor Systems Based on Toluene and Tetracyanoquinodimethane Derivatives

Modulation of Backbone Architecture to Design Structurally Durable Tetracyanoquinodimethane Derivatives with High Redox Activity

Modulation of Backbone Architecture to Design Structurally Durable Tetracyanoquinodimethane Derivatives with High Redox Activity

Synthesis, Structure, and Significant Energy Gap Modulation of Symmetrical Silafluorene-Cored Tetracyanobutadiene and Tetracyanoquinodimethane Derivatives.

A series of symmetrical tetracyanobutadiene and tetracyanoquinodimethane derivatives with a D-A-D'-A-D structural configuration and silafluorene core (D') were designed and readily synthesized via a [2+2] cycloaddition-retroelectrocyclization (CA-RE) reaction. We found that the photophysical properties and HOMO and LUMO energy levels and gaps of the silafluorene derivatives could be profoundly remolded through CA-RE reactions and modulated by varying the peripheral donor units from phenyl, m-dimethoxyphenyl, and N,N-dimethylaniline to triphenylamine groups. After CA-RE reactions, the HOMO-LUMO gaps of 1a-1j are in the range of 1.75-2.78 eV, with significant decreases of 0.52-1.46 eV compared to those of the parent silafluorene compounds 2a-2j. The intriguing crystal structures of 1f and 1j were analyzed and elucidated to show their unique potential porosity. The stability, electrochemical, and computational studies were systematically performed to unveil the reshaped electron-donating and -withdrawing nature in one molecular system. 1h-1j with peripherally strong amino donors exhibit an intense and broad intramolecular charge transfer absorption band in the near-infrared region from 550 to 900 nm. The molecular design and synthesis reported here broaden the types and fields of D-A molecular systems for potential applications in organic optoelectronic devices.

Design and Development of Distinct Tetracyanoquinodimethane Derivatives Exhibiting Dual Effect of Fluorescence and Anticancer Activity

AbstractTetracyanoquinodimethane (TCNQ) is known to react with primary/secondary amines to generate mono/di‐substituted TCNQ derivatives resulting in optical (fluorescence) and non‐linear optical characteristics. However, the choice of amine plays a key role in the sequel of certain material attributes. Nevertheless, demonstration of TCNQ derivatives, specifically obtained by reacting TCNQ with simple & small amine side chains of existing anticancer drugs, emerging in dual effect of fluorescence as well as anticancer activity, is not explored so far and has been still existing as a gap in TCNQ related research. Additionally, mono/di‐substituted TCNQ's owning strong fluorescence in solutions (∼10 to 104 order) than their solids are still lacking and are in need to be generated. In this regard, we aimed to synthesize straightforward TCNQ derivatives in single step by reacting TCNQ with specific (simple and small) amines being side chains of existing anticancer drugs (a contemporary design approach) and successfully obtained novel mono/di‐substituted TCNQ derivatives manifesting dual effect of fluorescence and anticancer activity. In this fashion, we have avoided the usage of bulky main moiety of an anticancer molecule, since our aim was not to use the total anticancer drug as such, like in a Pro‐drug preparation, but we intended to use the minimal part of an anticancer drug to invent novel TCNQ derivatives as anticancer active fluorophores. Wavelength of maximum emission for all the five potent molecules was within ∼525 nm‐696 nm. All compounds showed moderate anticancer activity against different cancer cell lines and IC50 values were in the range of 11 to 49 μM, when the synthesized novel compounds were tested in B16F10, MDA‐MB‐231 and A549 cell lines. Henceforth, this study has emanated in the first generation TCNQ derivatives as organic fluorescent anticancer active molecules.

Doping-related broadening of the density of states governs integer-charge transfer in P3HT

Molecular p-doping allows for an increase in the conductivity of organic semiconductors, which is regularly exploited in thermoelectric devices. Upon doping, integer and fractional charge transfer have been identified as the two competing mechanisms to occur, where the former is desired to promote the generation of mobile holes in the semiconductor host. In general, high dopant electron affinity is expected to promote integer-charge transfer, while strong coupling between the frontier molecular orbitals of dopant and host promotes fractional charge transfer instead. Here, we investigate the role that the width of the density of states (DOS) plays in the doping process by doping the conjugated polymer poly(3-hexylthiophene) (P3HT) with tetracyanoquinodimethane (TCNQ) derivatives of different electron affinities at a 2% dopant ratio. Cyclic voltammetry confirms that only the electron affinity of F4TCNQ (tetrafluorotetracyanoquinodimethane) exceeds the ionization energy of P3HT, while TCNQ and FTCNQ (2-fluoro-7,7,8,8-tetracyanoquinodimethane) turn out to have significantly lower but essentially identical electron affinities. From infrared spectroscopy, we learn, however, that ca. 88% of FTCNQ is ionized while all of TCNQ is not. This translates into P3HT conductivities that are increased for F4TCNQ and FTCNQ doping, but surprisingly even reduced for TCNQ doping. To understand the remarkable discrepancy between TCNQ and FTCNQ, we calculated the percentage of ionized dopants and the hole densities in the P3HT matrix resulting from varied widths of the P3HT highest occupied molecular orbital (HOMO)-DOS via a semi-classical computational approach. We find that broadening of the DOS can yield the expected ionization percentages only if the dopants have significantly different tendencies to cause energetic disorder in the host matrix. In particular, while for TCNQ the doping behavior is well reproduced if the recently reported width of the P3HT HOMO-DOS is used, it must be broadened by almost one order of magnitude to comply with the ionization ratio determined for FTCNQ. Possible reasons for this discrepancy lie in the presence of a permanent dipole in FTCNQ, which highlights that electron affinities alone are not sufficient to define the strength of molecular dopants and their capability to perform integer-charge transfer with organic semiconductors.

Distinct Tetracyanoquinodimethane Derivatives: Enhanced Fluorescence in Solutions and Unprecedented Cation Recognition in the Solid State.

Tetracyanoquinodimethane (TCNQ) is known to react with various amines to generate substituted TCNQ derivatives with remarkable optical and nonlinear optical characteristics. The choice of amine plays a crucial role in the outcome of molecular material attributes. Especially, mono/di-substituted TCNQ’s possessing strong fluorescence in solutions than solids are deficient. Furthermore, cation recognition in the solid-state TCNQ derivatives is yet undetermined. In this article, we present solution-enhanced fluorescence and exclusive solid-state recognition of K+ ion achieved through the selection of 4-(4-aminophenyl)morpholin-3-one (APM) having considerable π-conjugation and carbonyl (C=O) functionality, particularly in the ring. TCNQ when reacted with APM, in a single-step reaction, resulted in two well-defined distinct compounds, namely, 7,7-bis(4-(4-aminophenyl)morpholin-3-ono)dicyanoquinodimethane (BAPMDQ [1], yellow) and 7,7,8-(4-(4-aminophenyl)morpholin-3-ono)tricyanoquinodimethane (APMTQ [2], red), with increased fluorescence intensity in solutions than their solids. Crystal structure investigation revealed extensive C–H−π interactions and strong H-bonding in [1], whereas moderate to weak interactions in [2]. Surprisingly, simple mechanical grinding during KBr pellet preparation with [1, 2] triggered unidentified cation recognition with a profound color change (in ∼1 min) detected by the naked eye, accompanied by a drastic enhancement of fluorescence, proposed due to the presence of carbonyl functionality, noncovalent intermolecular interactions, and molecular assemblies in [1, 2] solids. Cation recognition was also noted with various other salts as well (KCl, KI, KSCN, NH4Cl, NH4Br, etc.). Currently, the recognition mechanism of K+ ion in [1, 2] is demonstrated by the strong electrostatic interaction of K+ ion with CO and simultaneously cation−π interaction of K+ with the phenyl ring of APM, supported by experimental and computational studies. Computational analysis also revealed that a strong cation−π interaction occurred between the K+ ion and the phenyl ring (APM) in [2] than in [1] (ΔGbinding calculated as ∼16.3 and ∼25.2 kcal mol–1 for [1] and [2], respectively) providing additional binding free energy. Thus, both electrostatic and cation−π interactions lead to the recognition. Scanning electron microscopy of drop-cast films showed microcrystalline “roses” in [1] and micro/nano “aggregates” in [2]. Optical band gap (∼3.565 eV) indicated [1, 2] as wide-band-gap materials. The current study demonstrates fascinating novel products obtained by single-pot reaction, resulting in contrasting optical properties in solutions and experiencing cation recognition capability exclusively in the solid state.

Synthesis and properties of tetracyanoquinodimethane derivatives

Abstract Two new aza-acenequinone derivatives 4 and 5 were prepared by cyclocondensation of diamines 2 and 3 with bis(triisopropylsilyl)-dialkynyl-l,2-dione 1. Further reactions of compounds 4 and 5 with malononitrile using the Lehnert reagent afforded corresponding tetracyanoquinodimethane (TCNQ) derivatives 6 and 7. Compounds 4, 6 and 7 were characterized by single crystal X-ray diffraction techniques. Compounds 6 and 7 were studied electrochemically and photochemically. Density functional theory (DFT) calculations on compounds 6 and 7 indicate that both compounds have the potential to be candidates for organic semiconductor materials.

Carbon-Bridged Phenylene-Vinylenes: On the Common Diradicaloid Origin of Their Photonic and Chemical Properties

In this paper, experimental and computational investigations are combined to analyze the impact of the diradical character in the photonic and chemical properties of two tetracyano quinodimethane derivatives of phenylene-vinylenes. The photonic properties are evaluated with high-level quantum-chemical calculations and are rationalized in the context of the four-level model typical of diradical molecules, including one triplet and three singlet states, whereas the diradical extent in the ground electronic state is shown to be the driving force for the dimerization reactions. To this end DFT, CASSCF, and CASPT2//CASSCF calculations are carried out and complemented with experimental UV–vis–NIR absorption and emission measurements, as a function of the temperature along with resonance Raman spectroscopy investigations. The study of diradical molecules with enhanced chemical stability in the framework of organic electronics is an important field of research in organic π-conjugated molecules with direct applica...

Valence engineering of ionic molecular crystals: monovalent–divalent phase diagram for biferrocene–tetracyanoquinodimethane salts

The valence state of ionic molecular solids composed of biferrocene derivatives (D) and tetracyanoquinodimethane (TCNQ) derivatives (A), either monovalent ([D]+[A2]−) or divalent ([D]2+[A2]2−), can be controlled by changing the redox potentials and molecular volumes of the components.

Tetrathiafulvalene-Tetracyanoquinodimethane Charge-Transfer Complexes Wired to Carbon Surfaces: Tuning of the Degree of Charge Transfer

Charge-transfer complexes involving tetrathiafulvalene (TTF) and tetracyanoquinodimethane (TCNQ) derivatives are engineered in a 2D arrangement onto a carbon surface through the exposure of immobilized TTF units to TCNQ compounds. TTF molecules were immobilized as robust monolayers on carbon surfaces using the electrografting method followed by a click chemistry coupling. When the TTF monolayer is exposed to TCNQ, TCNQF2 (2,5-difluoro-TCNQ), and TCNQF4 (2,3,5,6-tetrafluoro-TCNQ), strong donor–acceptor complexes are formed onto the surface. A considerable decrease of the electrochemical response accompanies the formation of the charge-transfer complex. This observation is rationalized by the analysis of original crystal samples using an ultramicroelectrode cavity, confirming that charge-transfer complexes are electrochemically silent. A fine control of the degree of charge transfer with the judicious choice of different acceptors is evidenced through electrochemical and X-ray photoelectron spectroscopy (XP...

Synthesis and structures of 11,11,12,12-tetracyano-2,6-diiodo-9,10-anthraquinodimethane and its 2:1 cocrystals with anthracene, pyrene and tetrathiafulvalene.

Radical salts and charge-transfer complexes (CTCs) containing tetracyanoquinodimethane (TCNQ) display electrical conductivity, which has led to the development of many TCNQ derivatives with enhanced electron-accepting properties that are applicable toward organic electronics. To expand the family of TCNQ derivatives, we report the synthesis and structures of 11,11,12,12-tetracyano-2,6-diiodo-9,10-anthraquinodimethane (abbreviated as DITCAQ), C20H6I2N4, and its charge-transfer complexes with various electron donors, namely DITCAQ-anthracene (2/1), C20H6I2N4·0.5C14H10, (I), DITCAQ-pyrene (2/1), C20H6I2N4·0.5C16H10, (II), and DITCAQ-tetrathiafulvalene (2/1), C20H6I2N4·0.5C6H4S4, (III). The molecular structure of DITCAQ consists of a 2,6-diiodo-9,10-dihydroanthracene moiety with two malononitrile substituents. DITCAQ possesses a saddle shape, since the malononitrile groups bend significantly up out of the plane of the central ring and the two benzene rings bend down out of the same plane. π-π interactions between DITCAQ and the electron-donor molecules control the degree of charge transfer in cocrystals (I), (II), and (III), which is reflected in both the dihedral angles between the terminal benzene ring and the central ring on the DITCAQ motifs, and their corresponding IR spectra.

Air-stable n-channel organic field-effect transistors based on charge-transfer complexes including dimethoxybenzothienobenzothiophene and tetracyanoquinodimethane derivatives

Novel mixed stack charge-transfer complexes (DMeO-BTBT)(Fn-TCNQ) show air-stable n-channel transistor performance in the thin films and single crystals.

Syntheses and properties of a new series of tetrathiafulvalene derivatives incorporating fused ethyleneoxymethylene and ethylenethiomethylene units, and their charge–transfer complexes

Nine tetrathiafulvalene (TTF) derivatives incorporating fused ethyleneoxymethylene (EOM) and ethylenethiomethylene (ETM) units were newly synthesized by self-coupling or cross-coupling reactions. Unsymmetrical ETMEDT-TTF (4) was also synthesized by a Wittig-type reaction. Crystal structural analysis of these neutral donors revealed specific intermolecular interactions between donors, and many S⋯S, O⋯H, and S⋯H short contacts. Electrochemical properties of these donors were investigated by cyclic voltammetry under two different measurement conditions. Electronic spectra of neutral donors in chloroform and some cation radicals in methanol and on KBr pellets were measured and discussed. A distribution of the highest occupied molecular orbital (HOMO) around the EOM and ETM moieties of these donors was not found. The introduction of EOM and ETM groups to the TTF skeleton only slightly modulated the HOMO energy. Some charge–transfer (CT) complexes of these donors with tetracyanoquinodimethane (TCNQ) derivatives were prepared. A needle crystal of the CT complex of EOMMDT-TTF (5) with TCNQ was metallic down to 102K with a high σRT value of 169Scm−1. TTF derivatives incorporating fused EOM groups were more effective in conductivity than those incorporating fused ETM groups.

Synthesis of glycoluril-tetrathiafulvalene molecular clips for electron-deficient neutral guests through a straightforward Diels–Alder strategy

An electroactive molecular clip incorporating tetrathiafulvalene (TTF) sidewalls grafted on a glycoluril platform has been synthesized using a straightforward Diels–Alder strategy. This way of attachment to the glycoluril U-shape scaffold afforded a rigidified and closed receptor for which the electron-rich TTF pincers are expected to be at a suitable distance for sandwiching neutral guests through donor–acceptor interactions. The efficient complexation ability of this host architecture toward one molecule of tetracyanoquinodimethane derivative (F4-TCNQ) in solution has been demonstrated using cyclic voltammetry and UV-Visible titration methods.

Charge‐Transfer Complex Crystal Based on Extended‐π‐Conjugated Acceptor and Sulfur‐Bridged Annulene: Charge‐Transfer Interaction and Remarkable High Ambipolar Transport Characteristics

A single crystal of a novel mixed-stack donor-acceptor complex formed by a tetracyanoquinodimethane derivative with an extended π-conjugated system and a sulfur-bridged annulene displays the highest ambipolar transport behavior among donor-acceptor complexes reported with electron and hole mobilities reaching up to 0.24 and 0.77 cm(2) V(-1) s(-1) , respectively.

Exploration of Charge-Transfer Solids Utilizing Nucleobases: Nanoarchitectures by Hydrogen-Bonds in the Ionic Assemblies of Guanine and TCNQ Derivatives

We studied formation and structural characteristics of charge-transfer solids of 9-n-butylguanine (BuG) with fluorinated tetracyanoquinodimethane derivatives (FnTCNQ, n = 4, 2, and 1). Complex formation in a methanol (MeOH)-containing solvent generated two types of salts composed of either a methoxy-substituted anion or a fully ionic anion radical of FnTCNQ. In all anion radical salts, BuG existed as a protonated or a hemiprotonated species, BuGH+ or (BuG)(BuGH+), respectively, and formed hydrogen-bonded (H-bonded) assemblies. In these BuGH+ assemblies, FnTCNQ•– molecules were fixed and aligned periodically, providing H-bonded polycationic templates. In (BuGH+)(F4TCNQ•–), BuGH+ dimers by complementary H-bonds formed a two-dimensional (2D) polycationic sheet. The F4TCNQ•– face-to-face dimers formed a one-dimensional (1D) segregated column aided by formation of H-bonds with BuGH+. In (BuGH+)(F2TCNQ•–)(MeOH), BuGH+ dimers by complementary double H-bonds formed a 1D polycationic ribbon supported by MeOH-media...

Complex Formation between a Nucleobase and Tetracyanoquinodimethane Derivatives: Crystal Structures and Transport Properties of Charge-Transfer Solids of Cytosine

Abstract Reaction between cytosine, a nucleobase, in methanol and several 7,7,8,8-tetracyanoquinodimethane derivatives (R-TCNQ) in acetonitrile yielded three kinds of ionic solids; (I) insulators composed of methoxy-substituted R-TCNQ anions, (II) semiconducting fully ionic R-TCNQ radical anion salts, and (III) conductive partially ionic or mixed-valent R-TCNQ radical anion salts. Electronic and chemical structures of these products were characterized by optical and magnetic measurements, and structural and elemental analyses. Cation units in all products were found to be protonated cytosine species. Crystal structures were determined for methoxy-substituted anion salts (R = F4 and H) in Group I and R-TCNQ radical anion salts (R = H and Et2) in Group II with hemiprotonated cytosine pairs formed by triple self-complementary hydrogen bonds. They established one-dimensional hemiprotonated cytosine ribbons by double complementary hydrogen bonds. Hydrogen bonds between cytosine and R-TCNQ anions exhibited high potential to regulate molecular arrangements producing a segregated layered structure and uniform arrangement of R-TCNQ radical anion columns stable down to low temperature. The partially ionic salt of MeTCNQ in Group III exhibited metallic behavior and the highest conductivity of 10+1 S cm−1 so far observed for charge-transfer complexes based on biological molecules.

Tetracyanoquinodimethane complexes of nickel(II) with an N,O-donor macrocycle

A nickel(II) chelate, NiL1Cl2, has been obtained by reaction of nickel(II) chloride with a 15-membered N,O-donor macrocyclic ligand. Single-crystal X-ray studies reveal an octahedral environment around nickel(II). 7,7′,8,8′-Tetracyanoquinodimethane (tcnq) derivatives of the nickel(II) chelate were prepared by reaction with Litcnq and Et3N(tcnq)2. Spectroscopic measurements show the presence of only anionic tcnq in [NiL1(tcnq)2]·4H2O and a mixture of non-coordinating anionic and neutral tcnq species in [NiL1](tcnq)4·H2O.

Tetracyanoquinodimethane derivatives of fully condensed schiff base ligands derived from 2,6-diacetylpyridine: crystal structure of a nickel(ii) chloride complex with 2,6-diacetylpyridinebis(semicarbazone)

The ligands 2,13-dimethyl-3,6,9,12,18-pentaaza-bicyclo[12.3.1]octadeca-1(17),2,12,14(18),15-pentaene (L1) and 2,6-diacetylpyridinebis(semicarbazone) (L2) give pentagonal bipyramidal complexes with some transition metal ions. The structure of [Ni-L2(H2O)2]Cl2·2H2O has been determined by single-crystal X-ray methods. Further reaction of complexes of L1 and L2 with the lithium salt of 7,7′,8,8′,-tetracyanoquinodimethane (tcnq) gives the corresponding adducts.