Solid state properties and molecular structure of some divalentnd10 cation-TCNQ salts

Fadly, M.; Gandoor, M. A. El; Sawaby, A.

doi:10.1007/bf01142029

Cited by 3 publications

(6 citation statements)

References 15 publications

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“…The electronic spectrum of neutral TCNQ contains two peaks at 380 and 400 nm, Figure (black trace). − The vibrational spectrum only includes one observable peak at 2224 cm –1 , Figure (black, simulated) and Figure (purple, measured), because the symmetric-asymmetric mode B has a very weak IR intensity in neutral TCNQ.…”

Section: Resultsmentioning

confidence: 99%

“…TCNQ 1– formed by electrochemical reduction or exposure to a very weakly interacting reductant such as decamethylferrocene (DFe), has three structured peaks at 850, 749, and 686 nm ,,,− and an additional peak at 445 nm , in its electronic spectrum, Figure (blue and green traces), and two peaks at approximately 2182 and 2156 cm –1 in the nitrile stretching region of its mid-IR spectrum, Figure (gray, simulated) and Figure (green, measured) . Frequency analysis of the TCNQ 1– molecule assigns these peaks to the IR-active modes B and C in Figure .…”

Section: Resultsmentioning

confidence: 99%

“…Within all of the binding geometries for both types of QDs, we believe that TCNQ interacts directly with surface Se ions, rather than coordinating to a surface Cd ion through the nitrile group and interacting indirectly with Se, for three reasons: (i) Our simulations show that the indirect interaction does not result in the distortion of the TCNQ molecule from planarity that is indicated by the IR spectra we measure (see the Supporting Information). (ii) It has been shown repeatedly that neutral TCNQ does not readily coordinate to Cd 2+ or other divalent cations; ,, rather, TCNQ must be prereduced chemically (i.e., added as a lithium salt) ,,, or the reaction driven electrochemically to induce coordination. (iii) The Cd 2+ on the surfaces of CdSe QDs is ligated by either octylphosphonate or octadecylphosphonate, which TCNQ does not displace.…”

Section: Resultsmentioning

confidence: 99%

“…(ii) It has been shown repeatedly that neutral TCNQ does not readily coordinate to Cd 2+ or other divalent cations; 8,9,40 rather, TCNQ must be prereduced chemically (i.e., added as a lithium salt) 9,18,21,40 or the reaction driven electrochemically 41 to induce coordination. (iii) The Cd 2+ on the surfaces of CdSe QDs is ligated by either octylphosphonate or octadecylphosphonate, which TCNQ does not displace.…”

Section: Formation Of Ct Complexes Of Tcnq and Electronmentioning

confidence: 99%

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Electronic and Vibrational Structure of Complexes of Tetracyanoquinodimethane with Cadmium Chalcogenide Quantum Dots

2014

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This paper describes the use of visible, near-infrared, and mid-infrared steadystate optical spectroscopy to study the geometries in which tetracyanoquinodimethane (TCNQ) adsorbs to the surfaces of highly cadmium enriched and near-stoichiometric CdSe quantum dots (QDs) in the formation of QD-TCNQ charge transfer (CT) complexes. Several TCNQ molecules are spontaneously reduced by chalcogenides on the surface of each CdSe QD. The degree of CT depends on the geometry with which the TCNQ adsorbs and the degree of distortion of TCNQ's geometry upon adsorption. Comparison of the electronic and vibrational spectra of CdSe QD-TCNQ complexes with those of CT complexes of TCNQ with molecular reductants (including molecular chalcogenides) and computer simulations of the geometries and vibrational spectra of the TCNQ-chalcogenide CT complexes show that (i) the Cd-enriched CdSe QDs reduce a factor of 7.4 more TCNQ molecules per QD than nearly stoichiometric CdSe QDs because surface selenides are more accessible in the Cdenriched QDs than in the near-stoichiometric QDs and (ii) TCNQ interacts with surface selenides through several adsorption modes that result in different amounts of charge transfer and different degrees of geometric distortion of TCNQ. This study provides a framework for determining the range of adsorption geometries of small molecules on QD surfaces, and for optimizing QD surfaces to adsorb molecules in configurations with maximal electronic coupling between the QD and the adsorbate. ■ INTRODUCTIONThis paper describes the use of visible, near-infrared, and midinfrared steady-state optical spectroscopy to determine the set of geometries in which tetracyanoquinodimethane (TCNQ) adsorbs to the surfaces of CdSe quantum dots (QDs) in the formation of QD-TCNQ charge transfer (CT) complexes, and the dependence of these geometries on the surface chemistry of the QDs. Metal-chalcogenide QDs have high absorption cross sections, for instance, factors of ten to 100 greater than that of the metal-to-ligand charge transfer absorption band of ruthenium(II)tris(bipyridine) (Ru(bpy) 3 2+ ), 1 for bandgapresonant excitations across the long-UV, visible, and nearinfrared regions of the solar spectrum. 2 This optical bandgap can be tuned with both the material and size of the QD. 2 They also have the ability to accumulate multiple simultaneous excitons or charge carriers within a single nanoparticle. These properties make QDs potentially important as chromophores and redox centers within photovoltaic and photocatalytic active materials. For both types of devices, efficient extraction of charge carriers from the QDs is critical to the performance of the device. We have shown previously that, in order for ultrafast (tens of picoseconds or faster) charge transfer between a QD and a molecule to occur, the molecule must permeate the ligand shell of the QD and adsorb, at least transiently, to its inorganic surface. 3,4 It is therefore important to know what types of surface chemistries promote adsorption of potential molecular redox p...

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Formation Of Ct Complexes Of Tcnq and Electronmentioning

confidence: 99%

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Electronic and Vibrational Structure of Complexes of Tetracyanoquinodimethane with Cadmium Chalcogenide Quantum Dots

2014

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“…In this paper we propose a new approach which may increase the options on all three of those fronts, through the formation of a TCNQ-based charge transfer salt. TCNQ (7,7,8,8-tetracyanoquinodimethane) is well known as an extremely strong organic electron acceptor, with an electron affinity of 2.88 eV, 32 and its anion TCNQ À is known to rapidly form stable charge transfer salts with almost any cation, whether metallic 33 or organic 34,35 in nature. In addition, it has two favorable redox peaks (À185 and +445 mV vs. NHE) 36 for interacting with both the stromal (À530 mV) and lumenal (+490 mV) sides of PSI.…”

Section: Introductionmentioning

confidence: 99%

A new platform for development of photosystem I based thin films with superior photocurrent: TCNQ charge transfer salts derived from ZIF-8

et al. 2020

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Current Oscillatory Phenomena Based on Redox Reactions at a Hanging Mercury Drop Electrode (HMDE) in Dimethyl Sulfoxide

2004

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A systematic and comprehensive study on cyclic voltammetric anodic current oscillation (CVACO) at a hanging mercury drop electrode (HMDE) was carried out for the redox reactions of molecular oxygen (O2), nitrobenzene (NB), 1,4-dinitrobenzene (DNB), benzoquinone (BQ), 2,3,5,6-tetramethylbenzoquinone (TMBQ), benzophenone (BP), azobenzene (AB), 2,1,3-benzothiadiazole (BTD), 7,7,8,8-tetracyanoquinodimethane (TCNQ), methyl viologen dichloride (MV2+), and tris(2,2‘-bipyridine)ruthenium(II) dichloride [Ru(bpy)3 2+] in dimethyl sulfoxide (DMSO) solutions containing 0.1 M tetraethylammonium perchlorate (TEAP). From the electrocapillary curve (ECC) obtained using a dropping mercury electrode as well as the capacitance versus potential curves measured using electrochemical impedance technique, the value of the potential of zero charge (PZC) was estimated to be −0.27 V versus Ag|AgCl|NaCl (sat.) in a DMSO solution containing 0.1 M TEAP. CVACO was found to occur only for the redox couples (i.e., BP0/BP•-, O2 0/O2 •-, AB0/AB•-, Ru(bpy)3 2+/Ru(bpy)3 +, BTD0/BTD•-, NB0/NB•-, DNB0/DNB•-, DNB•-/DNB2-, TMBQ0/TMBQ•-, MV2+/MV•+, and BQ•-/BQ2-) having the formal potentials (E 0‘ values) more negative than the PZC. CVACO was largely dependent on the concentrations of redox species and TEAP; for example, in the case of BTD the intensity of CVACO increased with increasing concentration, and CVACO ceased at high concentrations of TEAP (≥0.5 M). Furthermore, CVACO was not observed for the BQ0/BQ•- redox couple having E 0‘ (= −0.31 V) near the PZC, and a pronounced cathodic maximum was observed for the TCNQ•-/TCNQ2- redox couple with E 0‘ (= −0.16 V) more positive than the PZC. These observations and the factors governing the CVACO are discussed on the basis of the theory presented for the polarographic maxima of the first kind. The observed CVACO and the cathodic maximum obtained for the TCNQ•-/TCNQ2- redox couple could be explained in terms of the so-called streaming effect.

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Solid state properties and molecular structure of some divalentnd10 cation-TCNQ salts

Cited by 3 publications

References 15 publications

Electronic and Vibrational Structure of Complexes of Tetracyanoquinodimethane with Cadmium Chalcogenide Quantum Dots

Electronic and Vibrational Structure of Complexes of Tetracyanoquinodimethane with Cadmium Chalcogenide Quantum Dots

A new platform for development of photosystem I based thin films with superior photocurrent: TCNQ charge transfer salts derived from ZIF-8

Current Oscillatory Phenomena Based on Redox Reactions at a Hanging Mercury Drop Electrode (HMDE) in Dimethyl Sulfoxide

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