NMR Measurements Research Articles

Investigation of Host–Guest Interactions in 2-Ureido-4-ferrocenylpyrimidine Derivatives

In the present study, synthesis, conformational behavior, host–guest complex formation, and electrochemical properties of novel 6-substituted-2-ureido-4-ferrocenylpyrimidines were explored. A comprehensive NMR spectroscopic investigation was carried out to confirm the structure and conformational equilibrium of the ureidopyrimidines through studying the temperature- and concentration dependence of NMR spectra. Low-temperature NMR measurements were used to clarify structural changes inflicted by a 2,6-diaminopyridine guest. Association constant (Kassoc) values of host–guest complexes were calculated based on low-temperature titrations. It was shown that the introduction of a pyridin-2-yl substituent in the pyrimidine ring in host 10 induced a considerable change not only in the conformational equilibrium of the host itself but also in that of the host–guest complex. Geometries and relative stabilities of the conformers of host 10 as well as its host–guest complexes were determined by quantum chemical calculations. Electrochemical behavior of ureidopyrimidine hosts and host–guest complexes was investigated by cyclic voltammetry (CV) and linear sweep voltammetry (LSV) measurements. Two ureidopyrimidine derivatives were immobilized on the surface of spectral graphite electrodes, and their electrochemical response on the addition of 2,6-diaminopyridine was compared. These results also supported the importance of the pyridin-2-yl substituent in the efficient sensing of the guest.

Spontaneous nanosized liposome formation from crude dried lecithin upon addition of glycerol

Nanosized liposomal vesicles (NLV) were successfully prepared using natural sunflower lecithin without the use of high-pressure homogenization or filtration. Upon glycerol addition to dispersions of lecithin multilamellar vesicles (MLVs), these broke down spontaneously to liposomes with diameters in the range of 100–200 nm. Static light scattering demonstrated that glycerol addition above 30% (w/w) induced the complete transformation of MLVs into NLVs. Langmuir trough compression experiments showed a two-region compressional behavior. Upon 62% (w/w) glycerol addition, the compressional modulus of the liposomes decreased from 18.5 to 8.13 mN/m. Water activity and pulse NMR measurements also showed a divergence in behavior above 30% (w/w) glycerol. Liposomes were not birefringent in water but became strongly birefringent at and above 30% (w/w) glycerol, as determined by polarized light microscopy, and lost all birefringence above 80% (w/w). This was interpreted as the induction of stress-birefringence in the phospholipid bilayers above 30% (w/w) glycerol, and a relaxation of such stress above 80% (w/w) glycerol. We hypothesize that the mixture of phospholipids in the lecithin results in an effective non-zero intrinsic curvature for the molecular mixture, which lowers the bending energy of the bilayer, allowing for an easier break-up upon mixing. Secondly, glycerol addition decreases attractive van der Waals’ interaction between lamellae in an MLV, thus weakening the multilamellar liposome walls. Glycerol also affects bilayer stability by strengthening the hydrogen bond network of water, which will affect phospholipid headgroup hydration. All these factors result in the spontaneous breakdown of MLVs into NLVs.

Positive activation entropy of Bacillus circulans xylanase catalyzed ONPX2 hydrolysis: A mechanistic and engineering study

Transition state (TS) stabilization by enzymes greatly accelerates catalytic reactions. For some enzymes, the TS complex has entropy higher than enzyme substrate (ES) complex. But the origin of favorable entropy remains unclear. In this work, we studied the mechanism of Bacillus Circulans xylanase (BCX) 11 catalyzed o-nitrophenyl β-xylobioside (ONPX2) glycoside hydrolysis. The catalytic reaction exhibits a positive activation entropy, and an increase in ionic strength leads to a decrease in entropy without affecting the activation free energy, indicating that the entropy is predominantly influenced by electrostatic forces. Moreover, NMR measurements of electrostatic attractions within the active site demonstrate a positive entropy, aligning with molecular dynamics (MD) simulations showing that electrostatic interactions contribute to the entropic stabilization of the TS complex. These findings suggest that the positive entropy primarily originates from alterations in electrostatic interactions due to the formation of the oxocarbenium ion at C1 in the TS. Differences of electrostatic interactions in ES and TS modify hydrogen bonding of surrounding residues in the active site which causes their side chain dynamics and thus conformational entropy changes. Residues critical for the positive activation entropy are identified. A new BCX mutant with an increased activation entropy and catalytic activity is found.

Synthesis, characterization, and bioactivity of Cu(II), Fe(II), Co(II), Ni(II), and Mn(II) complexes with benzilmonoximethiocarbohydrazide-O-methoxybenzaldehyde: experimental and computational insights.

In this study, a novel ligand, benzilmonoximethiocarbohydrazide-O-methoxybenzaldehyde (HBMToMB), was synthesized and subsequently complexed with Cu(II), Fe(II), Co(II), Ni(II), and Mn(II) ions. The metal complexes were comprehensively characterized using techniques such as NMR, IR, Mass Spectrometry, UV-Vis, elemental analysis (CHNS), and magnetic susceptibility measurements. The complexes exhibited superior antibacterial and antifungal activity compared to the free ligand. In addition, cytotoxicity was evaluated using the brine shrimp lethality bioassay, demonstrating significant activity. Computational studies, including molecular docking, DFT, and ADMET analysis, provided further insights into the compounds' binding affinities and electronic properties. These findings underscore the potential of these metal complexes as promising candidates for therapeutic applications, particularly in antimicrobial and anticancer therapies.

Assessment of hydrogen adsorption in high specific surface geomaterials using low-field NMR - Implications for storage and field characterization

Natural and produced hydrogen will play a central role in decarbonizing the economy. High specific surface geomaterials can contribute H2 adsorption capacity, affecting both natural systems and storage strategies. Low-field Nuclear Magnetic Resonance NMR provides unique insights into H2 gas adsorption on nanoporous geomaterials. The cumulative NMR amplitude correlates linearly with the hydrogen mass; furthermore, measurements reveal two relaxations: a short-time relaxation for adsorbed H2 gas, and a long-time pressure-dependent relaxation for free H2 gas within pores. NMR measurements and complementary Grand Canonical Monte Carlo simulations show 2.5-to-4 times higher density in adsorbed H2 than bulk H2. The H2 adsorption capacity varies with mineral composition, but in all cases, it increases with specific surface area. Therefore, hydrogen physisorption in nanoporous geomaterials improves storability with respect to single-phase pure gas storage when high specific surface bentonites (at low pressure) or activated carbon (at all pressures) are the adsorbents. While synthetic adsorbents may exhibit higher H2 storage capacities, the low cost of high specific surface geomaterials, the reduced storage buoyancy, and safer controlled release make these natural adsorbents particularly attractive for large-scale storage applications. The insights gained with low-field NMR measurements in the laboratory are directly applicable to the interpretation of down-hole NMR characterization tools in the field.

A Novel Rhodamine B Fluorescent Probe Derived from Carboxymethyl Chitosan for the Selective Detection of Fe3.

In this study, we synthesized a fluorescent material by modifying the C-2 amino group of carboxymethyl chitosan with a rhodamine B derivative, which was proposed and demonstrated using 1H NMR and FT-IR measurements. A series of experiments including selectivity, sensitivity, reversibility, pH, and water content were conducted to investigate the fluorometric and colorimetric properties of the grafted polymer. Utilizing a Fe3+-induced ring-opening mechanism of the rhodamine B spirolactam, we found that the grafted polymer exhibited a highly selective fluorescence response to Fe3+, with enhanced fluorescence at 583 nm compared to other tested metal ions and anions, accompanied by the characteristic absorption peak of rhodamine B that appeared at 561 nm with a noticeable color change from colorless to pink, facilitating visual observation. Additionally, the modified probe, composed of carboxymethyl chitosan, was easily regenerated through treatment with EDTA.

Aktivierung von Kohlenstoff‐Kohlenstoff Bindungen durch Chrom(I): Spaltung von Dialkinen durch einen 11‐Elektronenkomplex

AbstractEin T‐förmiger Chrom(I)‐11‐Elektronenkomplex wurde durch Reduktion eines [PNP]‐stabilisierten Chrom(II)iodid‐Komplexes erhalten. Seine high‐spin d5‐Elektronenkonfiguration wurde mittels paramagnetischer NMR‐, EPR‐, UV/Vis‐ und magnetischer Messungen (SQUID) charakterisiert. Der Komplex reagiert leicht mit konjugierten Dialkinen unter Spaltung der internen C−C‐Bindung und Ausbildung des jeweiligen Acetylidkomplexes. Variation der Alkinsubstituenten ermöglichte die Isolierung und Charakterisierung von zweikernigen Dialkindichrom‐Intermediaten, die sich thermisch in die Produkte umwandeln.

Carbon-Carbon Bond Activation at Chromium(I): An 11-Electron Complex Cleaving Dialkynes.

An 11-electron T-shaped chromium(I) complex was obtained by reduction of a PNP-supported chromium(II) iodide complex. Its d5 high-spin electronic structure was characterized employing paramagnetic NMR, EPR, UV/Vis and magnetic measurements (SQUID). The complex readily reacts with conjugated dialkynes to cleave the internal C-C bond, forming the respective acetylide complexes. Varying the alkyne substituents enabled the isolation and characterization of dinuclear dialkynedichromium intermediates which thermally convert to the products.

A Double-walled Noncovalent Carbon Nanotube by Columnar Packing of Nanotube Fragments.

Herein, we report the synthesis of double-walled noncovalent carbon nanotubes (CNTs) through host-guest complexation of nanotube fragments and tube-forming crystal engineering. As the smallest fragment of double-walled CNTs, a host-guest complex of perfluorocycloparaphenylene (PFCPP) and carbon nanobelt (CNB) was synthesized by mixing them in solvents. The immediate complexation of the PF[12]CPP⸧(6,6)CNB complex with a remarkably high association constant (Ka) of 2×105 L/mol was observed. Time-dependent 1H NMR and thermogravimetry measurements revealed that the stability of (6,6)CNB was significantly improved by encapsulation. X-ray crystallography confirmed the robust belt-in-ring structure of this complex. As indicated by the short distance between PF[12]CPP and (6,6)CNB (2.8 Å), intermolecular orbital interactions exist between the belt and the ring, which were further supported by theoretical calculation and phosphorescence quenching experiments. While the PF[12]CPP⸧(6,6)CNB complex adopts various crystal packing structures, chloroform was discovered to be a magic "glue" solvent inducing one-dimensional alignment of the PF[12]CPP⸧(6,6)CNB complex to build an unprecedented double-walled noncovalent CNT structure.

A Double‐walled Noncovalent Carbon Nanotube by Columnar Packing of Nanotube Fragments

AbstractHerein, we report the synthesis of double‐walled noncovalent carbon nanotubes (CNTs) through host–guest complexation of nanotube fragments and tube‐forming crystal engineering. As the smallest fragment of double‐walled CNTs, a host–guest complex of perfluorocycloparaphenylene (PFCPP) and carbon nanobelt (CNB) was synthesized by mixing them in solvents. The immediate complexation of the PF[12]CPP⸧(6,6)CNB complex with a remarkably high association constant (Ka) of 2×105 L/mol was observed. Time‐dependent 1H NMR and thermogravimetry measurements revealed that the stability of (6,6)CNB was significantly improved by encapsulation. X‐ray crystallography confirmed the robust belt‐in‐ring structure of this complex. As indicated by the short distance between PF[12]CPP and (6,6)CNB (2.8 Å), intermolecular orbital interactions exist between the belt and the ring, which were further supported by theoretical calculation and phosphorescence quenching experiments. While the PF[12]CPP⸧(6,6)CNB complex adopts various crystal packing structures, chloroform was discovered to be a magic “glue” solvent inducing one‐dimensional alignment of the PF[12]CPP⸧(6,6)CNB complex to build an unprecedented double‐walled noncovalent CNT structure.

Liquid-Phase NMR of Humic and Fulvic Acids.

Present review focuses on the most recent advances in the NMR of the coal-derived humic and fulvic acids, covering exclusively the results of the liquid-phase NMR and leaving apart an overwhelming amount of publications dealing with the solid-state NMR investigations in this field (the latter are comprehensively reviewed elsewhere). Owing to the complexity of humic and fulvic acids together with other coal-derived products, their 1H and 13C NMR spectra consist of a number of overlapping signals belonging to different hydrocarbon types. Comprehensive studies of humic and fulvic acids by means of NMR revealed characteristic functional groups of their composition together with spectral regions in which they resonate. Quantitative 1H and 13C NMR spectra characterize aromatic and saturated carbons spread over many structural moieties, which provides a solid guideline into molecular structure of humic and fulvic acids together with parent coal-derived products. Nowadays, quantitative 13C NMR measurements yield information about a variety of structural parameters such as functional group distribution, aromaticity, degree of condensation of aromatic rings, and medium chain lengths together with many other more specific parameters. The structural NMR studies of the coal-derived products are developing on a background of a marked progress in experimental and computational NMR. Discussed in the present review are the most recent advances in the liquid-state NMR studies of the coal-derived humic and fulvic acids together with their processing products.

1H and 13C NMR and FTIR Spectroscopic Analysis of Formic Acid Dissociation Dynamics in Water.

The formation and transport of ionic charges in formic acid-water (HCOOH-H2O) mixtures with initial water mole fractions ranging from XH2Oi = 0 to 1 were investigated using 13C and 1H NMR, FTIR spectroscopy, viscosity, conductivity, and pH measurements. The maximum molar concentration of ions (H3O+ and HCOO-), along with the relative differences between theoretical and experimental densities, spin-lattice relaxation times (T1), activation energies (Ea), viscosity (η), and conductivity (σ), were identified within the range of XH2Oi ≈ 0.5-0.7. These results indicate that pure formic acid (FA) solutions predominantly consist of cyclic dimers at room temperature. As the water mole fraction increases up to 0.6, a structural shift occurs from cyclic dimers to a mixture of linear and cyclic dimers, driven by the formation of strong hydrogen bonds. Beyond a water mole fraction of 0.6, the structure transitions to linear dimers, with FA molecules behaving as free entities in the water. Furthermore, the acidity was found to increase approximately 2-fold with every 0.1 increment in water mole fraction. These findings are critical for understanding the kinetics of formic acid anions in body fluids, the structure of the hydrogen bonding network, and ionization energies.

Measuring 15N and 13C Enrichment Levels in Sparsely Labeled Proteins Using High-Resolution and Tandem Mass Spectrometry.

Isotope labeling of both 15N and 13C in selected amino acids in a protein, known as sparse labeling, is an alternative to uniform labeling and is particularly useful for proteins that must be expressed using mammalian cells, including glycoproteins. High levels of enrichment in the selected amino acids enable multidimensional heteronuclear NMR measurements of glycoprotein three-dimensional structure. Mass spectrometry provides a means to quantify the degree of enrichment. Mass spectrometric measurements of tryptic peptides of a selectively labeled glycoprotein expressed in HEK293 cells revealed complicated isotope patterns which consisted of many overlapping isotope patterns from intermediately labeled peptides, which complicates the determination of the label incorporation. Two challenges are uncovered by these measurements. Metabolic scrambling of amino groups can reduce the 15N content of enriched amino acids or increase the 15N in nontarget amino acids. Also, undefined, unlabeled medium components may dilute the enrichment level of labeled amino acids. The impact of this unexpected metabolic scrambling was overcome by simulating isotope patterns for all isotope-labeled peptide states and generating linear combinations to fit to the data. This method has been used to determine the percent incorporation of 15N and 13C labels and has identified several metabolic scrambling effects that were previously undetected in NMR experiments. Ultrahigh mass resolution is also utilized to obtain isotopic fine structure, from which enrichment levels of 15N and 13C can be assigned unequivocally. Finally, tandem mass spectrometry can be used to confirm the location of heavy isotope labels in the peptides.

Thermodynamic modeling of the structure of alkali aluminophosphate glasses and their ionic conductivity

AbstractThis study presents the structural and ionic conductivity thermodynamic modeling for glasses with compositions in the system 50M2O‐xAl2O3‐(50 − x)P2O5, with M = Li or K. The Shakhmatkin and Vedishcheva thermodynamic model (SVTDM), or associated solutions model, has been previously used in successfully predicting the structure of simple binary phosphate glasses and it has now been employed with the aim to discerning the model's capability to predict the structural changes induced in the phosphate network by the addition of alumina. The results have been furthermore validated through their comparison with literature experimental data on the structural characterization of the glasses by 31P NMR measurements as well as on ionic conductivity determined by impedance spectroscopy. Although this methodology demonstrates good agreement with experimental data on the structure of aluminophosphate glasses, some disparities persist, potentially arising from experimental uncertainties. However, SVTDM faces limitations, including the need for comprehensive knowledge of stable phases and their formation energies. Predictions of ionic conductivity, though promising, exhibit deviations from experimental values, attributed to factors such as the influence of the chemical environment on dielectric properties. To enhance accuracy in conductivity prediction, a deeper understanding of additional variables such as dielectric constant and attempt frequency is imperative.

PH-controlled-ion-mobility of Laponite-phosphate dispersion for physical hydrogel with improved mechanical properties and sensitivity to CO2

Self-assembled physical nanocomposite hydrogels based on bio-based poly(itaconic acid) and Laponite® nanoclays were prepared and tested as possible CO2 sensors in smart food packaging. The structure and mechanical properties of the fabricated hydrogels were controlled by changing the initial pH of the aqueous Laponite® dispersions stabilised by tetrasodium pyrophosphate. The dispersions were studied by SAXS and analysed using circular disc and fractal model to determine clay agglomeration tendency. Sodium and pyrophosphate ions mobility was investigated by 23Na and 31P 1D as well as spin-spin relaxation times T2 NMR measurements. The rheological behaviour of the produced hydrogels was studied by oscillatory shear measurements. It was found that decreasing the pH of the Laponite® nanodispersions up to 8 increases the strength of the physical interactions between the nanoclays, dispersant, and polyelectrolyte chains, which enables production of dimensionally stable and mechanically robust hydrogels. Their potential application as the CO2-sensitive matrix for construction of environmentally friendly colorimetric sensors was demonstrated showing the CO2 sorption capacity of 0.07 mmol CO2/g. A prototype device of hydrogel sensor was built and tested in a food packaging application to monitor the plum fruit respiration processes.

Absolute Quantification of Phenylbutanoids in Zingiber cassumunar Roxb. Rhizome by Quantitative 1H NMR.

Quantitative determination of pharmacologically active constituents in medicinal plants is critical for quality control. Due to the chemical complexity of the crude plant extracts, the presence of interfering compounds is often problematic for the unambiguous quantitation of the designed bioactive compounds. Considering the method of quantification, quantitative NMR spectroscopy (qNMR) has gained substantial popularity as a powerful and effective technique for both qualitative and quantitative analyses of natural products. The aim of this study is to develop a quantitative NMR method for quantifying the bioactive phenylbutanoids in Zingiber cassumunar rhizome crude extract. Quantitative 1H NMR (qHNMR) measurements were performed on a 600 MHz NMR spectrometer using an internal standard for the determination of the absolute quantities of four phenylbutanoids in Z. cassumunar rhizome crude extract. The direct quantification of four characteristic phenylbutanoids, i.e., (E)-1-(3',4'-dimethoxyphenyl)butadiene (DMPBD), (E)-1-(2',4',5'-trimethoxyphenyl)butadiene (TMPBD), (E)-4-(3',4'-dimethoxyphenyl)but-3-en-1-ol, and (E)-4-(3',4'-dimethoxyphenyl)but-3-en-1-yl acetate, in crude extract by qHNMR using an internal standard was achieved, with high specificity and sensitivity. The selected 1H NMR signals could unambiguously be assigned and did not overlap with other resonances, including the highly similar compounds DMPBD and TMPBD. The method is linear in the concentration range of 0.70-14.52 mg/mL, with a limit of quantification of 0.46-0.68 mg/mL. The RSD values of intraday and interday precisions are in the range of 0.23%-0.74% and 0.29%-0.52%, respectively. The average recoveries are 99.54%-100.18%. A rapid, accurate, and precise method using 1H NMR for the simultaneous quantitation of four phenylbutanoids in the crude extract of Z. cassumunar rhizome was developed and validated.

A Simple Regeneration Process Using a CO2-Switchable-Polarity Solvent for Cellulose Hydrogels.

Cellulose is one of the main components of plant cell walls, abundant on earth, and can be acquired at a low cost. Furthermore, there has been increasing interest in its use in environmentally friendly, carbon-neutral, sustainable materials. It is expected that the applications of cellulose will expand with the development of a simple processing method. In this study, we dissolved cellulose in aqueous N-butyl-N-methylpyrrolidinium hydroxide solution ([C4mpyr][OH]/H2O) and investigated the cellulose regeneration process based on changes in solubility upon application of CO2 gas. We investigated the effect of transformation of the anion chemical structure on cellulose solubility by flowing CO2 gas into [C4mpyr][OH]/H2O and conducted pH, FT-IR, and 13C NMR measurements. We observed that the changes in anion structure allowed for the modulation of cellulose solubility in [C4mpyr][OH]/H2O, thus establishing a simple and safe cellulose regeneration process. This regeneration process was also applied to enable the production of cellulose hydrogels. The hydrogel formed using this method was revealed to have higher mechanical strength than an analogous hydrogel produced using the same dissolution solvent with the addition of a cross-linker. The ability to produce cellulose-based hydrogels of different mechanical properties is expected to expand the possible applications.

Phonons reveal coupled cholesterol-lipid dynamics in ternary membranes

Experimental studies of collective dynamics in lipid bilayers have been challenging due to the energy resolution required to observe these low-energy phonon-like modes. However, inelastic x-ray scattering (IXS) measurements—a technique for probing vibrations in soft and biological materials—are now possible with sub-meV resolution, permitting direct observation of low-energy, phonon-like modes in lipid membranes. Here, IXS measurements with sub-meV energy resolution reveal a low-energy optic-like phonon mode at roughly 3 meV in the liquid-ordered (Lo) and liquid-disordered phases of a ternary lipid mixture. This mode is only observed experimentally at momentum transfers greater than 5 nm−1 in the Lo system. A similar gapped mode is also observed in all-atom molecular dynamics (MD) simulations of the same mixture, indicating that the simulations accurately represent the fast, collective dynamics in the Lo phase. Its optical nature and the Q range of the gap together suggest that the observed mode is due to the coupled motion of cholesterol-lipid pairs, separated by several hydrocarbon chains within the membrane plane. Analysis of the simulations provides molecular insight into the origin of the mode in transient, nanoscale substructures of hexagonally packed hydrocarbon chains. This nanoscale hexagonal packing was previously reported based on MD simulations and, later, by NMR measurements. Here, however, the integration of IXS and MD simulations identifies a new signature of the Lo substructure in the collective lipid dynamics, thanks to the recent confluence of IXS sensitivity and MD simulation capabilities.

13C NMR studies and orientational order of rod-like mesogens with strongly polar terminal cyano group

ABSTRACT 13C NMR studies of two rod-like mesogens with core units consisting of two and three phenyl rings with strongly polar terminal cyano groups are reported. The two-ring mesogen displayed an enantiotropic smectic A (SmA) mesophase while for the three-ring mesogen, enantiotropic nematic and SmA mesophases were observed. The solution 13C NMR studies of both the mesogens are carried out besides static 13C NMR measurements in the liquid crystalline phase. For the two-ring mesogen, the chemical shift anisotropy (CSA) tensors of the core unit are determined by the 2D-separation of undistorted powder patterns by effortless recoupling (SUPER) experiment. Furthermore, 2D-separated local field (SLF) measurements are realised for both the mesogens in the liquid crystalline phase to determine the 13C-1H dipolar couplings to find the orientational order parameters of the phenyl rings. The main order parameter (Szz) of the two-ring mesogen varies from 0.63 to 0.53 across the SmA phase and for the three-ring mesogen, the Szz values are found to be ~0.73 in the SmA phase and ~0.69 in the nematic phase. The CSA values determined from the SUPER experiment are expected to be a significant utility for molecules with polar terminal nitro/cyano groups as ferroelectric nematic phases are realised in them.

Luminescent anthracene-based elastic mixed molecular crystals for flexible and FRET-assisted optical waveguides

Abstract Optical waveguides based on elastic molecular crystals are of interest as flexible and compact optical communication materials. Low emission efficiency is often a problem in terms of communication signal strength, and an increase in the loss factor α due to fluorescence reabsorption in the crystal reduces the photon transport efficiency. Here, we report the development and improvement of Förster resonance energy transfer (FRET)-assisted optical waveguides using anthracene-based elastic mixed molecular crystals. 9,10-Dicyanoanthracene was selected as the dopant for solution-grown crystallization of 9,10-dibromoanthracene. 1H NMR measurements of the obtained crystals showed that the acceptor doping to be 1% to 5%. Elastic behavior was observed even when doped with a few percent of the acceptor. The quantum efficiency was 0.016, a dramatic improvement over the previous luminescent elastic mixed molecular crystals (0.004). The α value (92 dB/cm) of this crystal containing 1%-doped 9,10-dicyanoanthracene is much lower than that of the crystal consisting of only 9,10-dibromoanthracene (1258 dB/cm) due to the reduced reabsorption in the FRET system. We have demonstrated a practical approach toward developing improved fluorescent, highly efficient, and flexible optical waveguides by constructing the mixed crystal structure by selecting appropriate acceptor molecules and their low doping ratios.