Abstract:The powder Raman spectra and the polarized infrared absorption spectra of a polycrystalline oriented film of (1:1) CT complex of 5,10-dihydro-5,10-dimethylphenazine (M2P) with 7,7,8,8-tetracyanoquinodimethane (TCNQ) are reported together with the polarized reflectance infrared spectra of a mosaic of single crystals [(010) crystal face] and the conductivity spectra obtained from a Kramers–Krönig analysis of the reflectance data. The powder Raman and infrared spectra of M2P–TCNQF4 and their temperature dependenc… Show more
“…Within the frequency range from 750 ± 1050 cm À1 , the n Ä 6 band was clearly defined at 951 cm À1 . [30] Increase in this band was demonstrated by measuring at lower temperatures, namely 270, 150, and 20 K (i) (Figure 3 c, Spectra iii, ii, i, respectively). The appearance of these a g -bands is direct evidence for TCNQ lattice dimerization at low temperatures.…”
Section: Resultsmentioning
confidence: 99%
“…The appearance of these a g -bands is direct evidence for TCNQ lattice dimerization at low temperatures. [30] Lattice dimerization was strongly associated with the electrical conducting behavior (see below).…”
The Bingel addition of a trimalonate derived from a chiral, cyclotriveratrylene (CTV)‐based tripodal tether to C60 was reinvestigated. The present use of enantiomerically pure (P)‐ and (M)‐configured CTV units in the tether allowed the isolation of a total of four enantiomerically pure C3‐symmetric tris‐adducts of [60]fullerene (two from each CTV enantiomer). With the support of NMR and UV/Vis spectroscopy, electronic (ECD) and vibrational (VCD) circular dichroism spectroscopic analysis (comparison to ECD data of known compounds and to ECD and VCD data calculated by TD‐DFT or ZINDO methods as part of this work) allowed a definitive determination of the following structural features for all four CTV‐C60 conjugates: (i) The constitution of the fullerene addition pattern, (ii) its absolute configuration, and (iii) the absolute configuration of the CTV moiety. It is concluded that the triple Bingel addition proceeded with complete regioselectivity and negligible diastereoselectivity, affording only the trans‐3,trans‐3,trans‐3 fullerene addition pattern in both enantiomeric forms, whereas the previously reported e,e,e motif was not formed.
“…Within the frequency range from 750 ± 1050 cm À1 , the n Ä 6 band was clearly defined at 951 cm À1 . [30] Increase in this band was demonstrated by measuring at lower temperatures, namely 270, 150, and 20 K (i) (Figure 3 c, Spectra iii, ii, i, respectively). The appearance of these a g -bands is direct evidence for TCNQ lattice dimerization at low temperatures.…”
Section: Resultsmentioning
confidence: 99%
“…The appearance of these a g -bands is direct evidence for TCNQ lattice dimerization at low temperatures. [30] Lattice dimerization was strongly associated with the electrical conducting behavior (see below).…”
The Bingel addition of a trimalonate derived from a chiral, cyclotriveratrylene (CTV)‐based tripodal tether to C60 was reinvestigated. The present use of enantiomerically pure (P)‐ and (M)‐configured CTV units in the tether allowed the isolation of a total of four enantiomerically pure C3‐symmetric tris‐adducts of [60]fullerene (two from each CTV enantiomer). With the support of NMR and UV/Vis spectroscopy, electronic (ECD) and vibrational (VCD) circular dichroism spectroscopic analysis (comparison to ECD data of known compounds and to ECD and VCD data calculated by TD‐DFT or ZINDO methods as part of this work) allowed a definitive determination of the following structural features for all four CTV‐C60 conjugates: (i) The constitution of the fullerene addition pattern, (ii) its absolute configuration, and (iii) the absolute configuration of the CTV moiety. It is concluded that the triple Bingel addition proceeded with complete regioselectivity and negligible diastereoselectivity, affording only the trans‐3,trans‐3,trans‐3 fullerene addition pattern in both enantiomeric forms, whereas the previously reported e,e,e motif was not formed.
“…Beyond the critical concentration y c $ 0.11, the temperature at ionicity change (filled circles) does not coincide with that at e-maximum (T m , open squares). ployed for TCNQ (b 1u m 20 mode) [80] and tetrafluoro-TCNQ (b 1u m 19 and b 2u m 33 modes) [81], we estimated q from the C@C stretch modes, which appear to show relatively large shift Dx for Et 2 TCNQ (x (0) /Dx = 1549/À37 and 1520/À48 cm À1 ), ClMeTCNQ (1539/À23 and 1528/ À26 cm À1 ), and FMeTCNQ (1562/À33 and 1539/ À24 cm À1 ). The q was calculated from frequency of the mode with the larger Dx.…”
“…[1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20] These organic CT complexes are classified into two types according to their different stacking styles of donor and acceptor molecules, i.e. the so-called segregated-stack and mixed-stack forms.…”
The dependence of thermal behaviors on the number of layers in Langmuir-Blodgett (LB) films of the mixedstack charge transfer (CT) complex of 7,8, doped by 3,3′,5,5′-tetramethylbenzidine (TMB) has been investigated by using ultraviolet-visible-near infrared (UV-vis-NIR) and infrared (IR) spectroscopies. The appearance of a broad CT absorption band in the NIR region reveals that the mixed-stack CT films are formed by donor doping. The degree of the charge transfer determined by a shift of the CtN stretching band of the TCNQ chromophore verifies that the CT complex films are in a quasi-neutral state. Their temperature-dependent UV-vis-NIR and IR spectra show that donor molecules (TMB) dedope from the CT complexes in the LB films, resulting in the restoration of acceptor molecules (octadecyl-TCNQ) to their neutral states at their respective dedope temperatures. The dedope temperature of the CT complex films increases with the number of layers up to a seven-layer film. Both the UV-vis-NIR and IR spectra show that the one-layer CT complex film undergoes a progressive thermal process. In contrast, the seven-and 11-layer films are stable up to 120°C and show rather abrupt changes near their dedope temperatures. Furthermore, pre-dedope phenomena are observed for the multilayer CT complex films but not for the one-layer CT film. This dependence of the thermal behaviors of the CT films on the number of layers may be attributed to the differences in the film thickness, the longitudinal interactions between the one-dimensional needle-like microcrystals of the CT complex, and the effects of the interaction between the first layer and a CaF 2 substrate.
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