Synthetic Receptors for the High‐Affinity Recognition of O‐GlcNAc Derivatives

The combination of a pyrenyl tetraamine with an isophthaloyl spacer has led to two new water‐soluble carbohydrate receptors (“synthetic lectins”). Both systems show outstanding affinities for derivatives of N‐acetylglucosamine (GlcNAc) in aqueous solution. One receptor binds the methyl glycoside GlcNAc‐β‐OMe with K_a≈20 000 m ^?1, whereas the other one binds an O‐GlcNAcylated peptide with K_a≈70 000 m ^?1. These values substantially exceed those usually measured for GlcNAc‐binding lectins. Slow exchange on the NMR timescale enabled structural determinations for several complexes. As expected, the carbohydrate units are sandwiched between the pyrenes, with the alkoxy and NHAc groups emerging at the sides. The high affinity of the GlcNAcyl–peptide complex can be explained by extra‐cavity interactions, raising the possibility of a family of complementary receptors for O‐GlcNAc in different contexts.     

Remarkably selective recognition of iodobenzene derivatives by a macrocyclic bis-Pt(II) metallohost

We designed and synthesized self‐assembled bis‐Pt^II dimer 1? 4 BF₄ with quino[8,7‐b][1,10]phenanthroline as an extended π‐face contact area, which acts as the first artificial receptor with high affinity toward iodinated aromatic compounds significantly based on noncovalent iodine ??? aromatic‐plane interactions in a “side‐on” fashion. Despite their structural similarity to a previously reported metallohost 2 ⁴⁺ that bears 2,2′:6′,2′′‐terpyridine units, a dramatic change in selectivity toward substituted benzene derivatives was observed for 1 ⁴⁺. ¹H NMR spectroscopic titration revealed a high affinity of 1 ⁴⁺ towards haloarenes, with exceptionally large association constants for 2‐iodophenol (K_a=16 000 M ^?1) and 1,2‐diiodobenzene (K_a=21 000 M ^?1), which are 93‐ and 140‐fold higher, respectively, than the values obtained for 2 ⁴⁺. In addition, 1 ⁴⁺ showed a remarkably high affinity and selectivity toward 2,6‐diiodophenol (K_a=35 000 M ^?1), which is an important substructure of the thyroid hormone T₄. X‐ray crystallography and theoretical calculations strongly suggest that “side‐on” iodine ??? aromatic‐plane interactions and π–π stacking contribute to the strong 1,2‐diiodobenzene and 2,6‐diiodophenol binding. The results obtained here give unique and valuable insight into the nature of halogen atom interactions in their “side‐on” region with an electropositive aromatic plane, which may provide useful guidance for designing artificial receptors for iodinated biomolecules.     

N‐Alkyl Ammonium Resorcinarene Salts as High‐Affinity Tetravalent Chloride Receptors

N‐Alkyl ammonium resorcinarene salts (NARYs, Y=triflate, picrate, nitrate, trifluoroacetates and NARBr) as tetravalent receptors, are shown to have a strong affinity for chlorides. The high affinity for chlorides was confirmed from a multitude of exchange experiments in solution (NMR and UV/Vis), gas phase (mass spectrometry), and solid‐state (X‐ray crystallography). A new tetra‐iodide resorcinarene salt (NARI) was isolated and fully characterized from exchange experiments in the solid‐state. Competition experiments with a known monovalent bis‐urea receptor ( 5 ) with strong affinity for chloride, reveals these receptors to have a much higher affinity for the first two chlorides, a similar affinity as 5 for the third chloride, and lower affinity for the fourth chloride. The receptors affinity toward chloride follows the trend K₁?K₂?K₃≈ 5 >K₄, with K_a=5011 m ^?1 for 5 in 9:1 CDCl₃/[D₆]DMSO.     

“Complex” versus “free radical” mechanism for the catalytic decomposition of H2O2 by ferric ions

Kinetic and spectrophotometric measurements made during the Fe³⁺ ion catalyzed decomposition of H₂O₂ have been analyzed using the computer simulation method. Improved values of the rate constants of the “complex scheme” and of the molar absorptivities ofthe intermediates were obtained: k₃/K_M = 4.94 M^?1 min^?1, k₄ = 193 M^?1 min^?1, ε_I/K_M = 52.3 M^?2 cm^?1, ε_II = 25.7 M^?1 cm^?1. The simulation revealed details of the reaction which were unavailable by other means and which explained several features of its kinetics. The total amount of O₂ evolved in the reaction using [H₂O₂] ～ 10^?2 M has been calculated and found to be nearly stoichiometric. O₂ evolution experiments in this region cannot, thus, distinguish between the “complex mechanism” predicting nearly stoichiometric evolution of O₂ and the “free radical mechanism” predicting exactly stoichiometricamounts of O₂. There are discrepancies within the “free radical scheme” with regard to the correct values of the rate constants to fit the reactions of H₂O₂ both with Fe²⁺ and Fe³⁺ ions, as well as other reactions assumed to proceed via free radicals.     

Gem‐dinitromethyl‐substituted Energetic Metal–Organic Framework based on 1,2,3‐Triazole from in situ Controllable Synthesis

Synthesizing energetic metal–organic frameworks at ambient temperature and pressure has been always a challenge in the research area of energetic materials. In this work, through in situ controllable synthesis, energetic metal–organic framework gem‐dinitromethyl‐substituted dipotassium 4,5‐bis(dinitromethyl)‐1,2,3‐triazole with a “cage‐like” crystal packing was obtained and characterized. Most importantly, for the first time, we found that it could be successfully afforded with a catalytic effect of trifluoroacetic acid. This new compound exhibited its high density (2.04 g cm^?3) at ambient temperature, superior detonation velocity (8715 m s^?1) to that of lead azide (5877 m s^?1) and comparable to that of RDX (8748 m s^?1). Its detonation products are mainly N₂ (48.1 %), suggesting it is also a green energetic material. The above‐mentioned performance indicates its potential applications in detonator devices as lead‐free primary explosive.     

Gadolinium(III)‐Hydroxy Ladders Trapped in Succinate Frameworks with Optimized Magnetocaloric Effect

Two kinds of inorganic gadolinium(III)‐hydroxy “ladders”, [2×n] and [3×n], were successfully trapped in succinate (suc) coordination polymers, [Gd₂(OH)₂(suc)₂(H₂O)]_n ? 2n H₂O ( 1 ) and [Gd₆(OH)₈(suc)₅(H₂O)₂]_n ? 4n H₂O ( 2 ), respectively. Such coordination polymers could be regarded as alternating inorganic–organic hybrid materials with relatively high density. Magnetic and heat capacity studies reveal a large cryogenic magnetocaloric effect (MCE) in both compounds, namely (ΔH=70 kG) 42.8 J kg^?1 K^?1 for complex 1 and 48.0 J kg^?1 K^?1 for complex 2 . The effect of the high density is evident, which gives very large volumetric MCEs up to 120 and 144 mJ cm^?3 K^?1 for complexes 1 and 2 , respectively.     

Evidence for a Rapid Degenerate Hetero‐Cope‐Type Rearrangement in [Cp*W(S)2S‐CH2‐CHCH2]

Treatment of the salt [PPh₄]⁺[Cp*W(S)₃]^? ( 6 ) with allyl bromide gave the neutral complex [Cp*W(S)₂S‐CH₂‐CH?CH₂] ( 7 ). The product 7 was characterized by an X‐ray crystal structure analysis. Complex 7 features dynamic NMR spectra that indicate a rapid allyl automerization process. From the analysis of the temperature‐dependent NMR spectra a Gibbs activation energy of ΔG^≠ (278 K)≈13.7±0.1 kcal mol^?1 was obtained [ΔH^≠≈10.4±0.1 kcal mol^?1; ΔS^≠≈?11.4 cal mol^?1 K^?1]. The DFT calculation identified an energetically unfavorable four‐membered transition state of the “forbidden” reaction and a favorable six‐membered transition state of the “Cope‐type” allyl rearrangement process at this transition‐metal complex core.     

A High-Affinity “Synthavidin” Receptor for Squaraine Dyes

Strong-binding host–guest pairings in aqueous media have potential as “supramolecular glues” in biomedical techniques, complementing the widely-used (strept)avidin-biotin combination. We have previously found that squaraine dyes are bound very strongly by tetralactam macrocycles possessing anthracenyl units as cavity walls. Here we show that replacing the anthracenes with pentacyclic 5,7,12,14-tetrahydro-5,7,12,14-tetraoxapentacene (TOP) units generates receptors which bind squaraines with increased affinities (around K_a=10¹⁰ m ⁻¹) and improved selectivities. Binding can be followed through changes to squaraine fluorescence and absorbance. The TOP units are easy to prepare and potentially variable, while the TOP-based receptor shows improved photostability, both in itself and in complex with squaraines. The results suggest that this system could prove valuable in the further development of practical “synthavidin” chemistry.     

Nanofibrillar Cellulose‐Chitosan Composite Film Electrodes: Competitive Binding of Triclosan,Fe(CN)63−/4−, and SDS Surfactant

Glassy carbon electrodes are modified with a thin film of a cellulose‐chitosan nanocomposite. Cellulose nanofibrils (of ca. 4 nm diameter and 250 nm length) are employed as an inert backbone and chitosan (poly‐D ‐glucosamine, low molecular weight, 75–85% deacetylated) is introduced as a structural binder and “receptor” or molecular binding site. The composite films are formed in a solvent evaporation method and prepared in approximately 0.8 μm thickness. The adsorption of three molecular systems into the cellulose‐chitosan films is investigated and approximate Langmuirian binding constants are evaluated: i) Fe(CN)₆^4? (K_Ferrocyanide=2.2×10³ mol^?1 dm³ in 0.1 M phosphate buffer at pH 6) is observed to bind to ammonium chitosan functionalities (present at pH<7), ii) triclosan (K_Triclosan=2.6×10³ mol^?1 dm³ in 0.1 M phosphate buffer pH 9.5) is shown to bind only weakly and under alkaline conditions, and iii) the anionic surfactant dodecylsulfate (K_SDS=3.3×10⁴ mol^?1 dm³ in 0.1 M phosphate buffer pH 6) is shown to bind relatively more strongly in acidic media. The competitive binding of Fe(CN)₆^4? and dodecylsulfate anions is proposed as a way to accumulate and indirectly determine the anionic surfactant.     

Sugar‐Decorated Sugar Vesicles: Lectin–Carbohydrate Recognition at the Surface of Cyclodextrin Vesicles

An artificial glycocalix self‐assembles when unilamellar bilayer vesicles of amphiphilic β‐cyclodextrins are decorated with maltose and lactose by host–guest interactions. To this end, maltose and lactose were conjugated with adamantane through a tetra(ethyleneglycol) spacer. Both carbohydrate–adamantane conjugates strongly bind to β‐cyclodextrin (K_a≈4×10⁴ M ^?1). The maltose‐decorated vesicles readily agglutinate (aggregate) in the presence of the lectin concanavalin A, whereas the lactose‐decorated vesicles agglutinate in the presence of peanut agglutinin. The orthogonal multivalent interaction in the ternary system of host vesicles, guest carbohydrates, and lectins was investigated by using isothermal titration calorimetry, dynamic light scattering, UV/Vis spectroscopy, and cryogenic transmission electron microscopy. It was shown that agglutination is reversible, and the noncovalent interaction can be suppressed and eliminated by the addition of competitive inhibitors, such as D ‐glucose or β‐cyclodextrin. Also, it was shown that agglutination depends on the surface coverage of carbohydrates on the vesicles.     

Cobalt(II) porphyrin axially coordinated with 2′-(pyridin-4-yl)-5′-(pyridin-2-yl)-1′-(pyridin-2-ylmethyl)-2′,4′-dihydro-1′H-pyrrolo[3′,4′ : 1,2](C60-Ih)[5,6]fullerene: formation,chemical structure,and spectroscopic properties

Construction of new effective photovoltaic devices based on organic dyes has important implications for modern and future technologies. In this article, we studied the equilibrium, the rate, and the spectral manifestation of the reaction of [(2,3,7,8,12,18-hexamethyl,13,17-diethyl,5-(2-pyridyl)porphyrinato)cobalt(II)]–[2′-(pyridin-4-yl)-5′-(pyridin-2-yl)-1′-(pyridin-2-ylmethyl)-2′,4′-dihydro-1′H-pyrrolo[3′,4′ : 1,2](C₆₀-I_h)[5,6]fullerene] triad formation as well as its spectral properties and photo electrochemical behavior. The cobalt porphyrin–pyridyl-substituted fullerene mixtures in toluene are self-assembling systems due to axial donor–acceptor binding between Co of the porphyrin complex and N-pyridyl of the substituted fullerene. The formation rate constant, k^298K, and the stability constant, K^298K, of donor–acceptor triad formed by coordination of two substituted fullerene molecules to Co porphyrin are (44.4 ± 0.8) mol L^?1 s^?1 and (56 ± 16)×10⁷ L² mol^?2, respectively. Modification of the titanium electrode coated with the natural oxide film was carried out using the porphyrin–fullerene triad and its individual components. Photopotential and photocurrent density of the system with modified electrode were studied. The obtained results are of interest for creating porphyrin-based donor–acceptor systems as components in organic photovoltaics.     

Ruthenium(III)-Phthalocyanine: Darstelllung und Eigenschaften von Di(halogeno)phthalocyaninato(1−)ruthenium(III), [Ru(X)2Pc] (X = Cl,Br, I)

Ruthenium(III) Phthalocyanines: Synthesis and Properties of Di(halo)phthalocyaninato(1?)ruthenium(III) Di(halo)phthalocyaninato(1?)ruthenium(III), [Ru(X)₂Pc^?] (X = Cl, Br, I) is prepared by oxidation of [Ru(X)₂Pc^2?]^? (Cl, Br, OH) with halogene in dichloromethane. The magnetic moment of [Ru(X)₂Pc^?] is 2,48 μ_B (X = Cl) resp. 2,56 μ_B (X = Br) in accordance with a systeme of two independent spins (low spin Ru^III and Pc^?: S = 1/2). The optical spectra of the red violet solution of [Ru(X)₂Pc^?] (Cl, Br) are typical for the Pc^? ligand with the “B” at 13.5 kK, “Q₁” at 19.3 kK and “Q₂ region” at 31.9 kK. Sytematic spectral changes within the iron group are discussed. The presence of the Pc^? ligand is confirmed by the vibrational spectra, too. Characteristic are the metal dependent bands in the m.i.r. spectra at 1 352 and 1 458 cm^?1 and the strong Raman line at 1 600 cm^?1. The antisymmetric Ru? X stretch (v_as(Ru? X)) is observed at 189 cm^?1 (X = I) resp. 234 cm^?1 (X = Br). There are two interdependent bands at 295 and 327 cm^?1 in the region expected for v_as(Ru? Cl) attributed to strong interaction of v_as(Ru? Cl) with an out-of-plane Pc^? tilting mode of the same irreducible representation. Only the symmetric Ru? Br stretch at 183 cm^?1 is selectively enhanced in the resonance-Raman(RR) spectra. The Raman line at 168 cm^?1 of the diiodo complex is assigned to loosely bound iodine. The broad band at 978 cm^?1 in the RR spectra of the dichloro complex is due to an intraconfigurational transition within the electronic ground state of low spin Ru^III split by spin orbit coupling.     

Spectroscopic Studies on the Simple Rcooh System

The carbonyl stretching vibration of monocarboxylic acid in CCl₄ solution has been investigated. We introduce a new “m-factor” to study the polymerization of this simple RCOOH system. The value of “m-factor” was evaluated and tested in different concentrations and temperatures. Three classes of acid polymers were found as followings: linear dimer in class I (m?2); linear and cyclic dimers in class II (m?4); linear, cyclic dimers, and linear trimer in class III (m?8). A linear relationship between log K₁ and (??1)/(2?+1) was found.     

Electrochemical investigation of the chemical diffusion,partial ionic conductivities,and other kinetic parameters in Li3Sb and Li3Bi

The galvanostatic intermittent titration technique (GITT) has been used to electrochemically determine the chemical and component diffusion coefficients, the electrical and general lithium mobilities, the partial lithium ionic conductivity, the parabolic tarnishing rate constant, and the thermodynamic enhancement factor in “Li₃Sb” and “Li₃Bi” as a function of stoichiometry in the temperature range from 360 to 600°C. LiCl, KCl eutectic mixtures were used as molten salt electrolytes and Al, “LiAl” two-phase mixtures as solid reference and counterelectrodes. The stoichiometric range of the antimony compound is rather small, 7 × 10^?3 at 360°C, whereas the bismuth compound has a range of 0.22 (380°C), mostly on the lithium deficit side of the ideal composition. The thermodynamic enhancement factor in “Li₃Sb” depends strongly on the stoichiometry, and has a peak value of nearly 70 000; for “Li₃Bi” it rises more smoothly to a maximum of 360. The chemical diffusion coefficient for “Li₃Sb” is 2 × 10^?5 cm² sec^?1 at negative deviations from the ideal stoichiometry and increases by about an order of magnitude in the presence of excess lithium at 360°C. The corresponding value for “Li₃Bi” is 10^?4 cm² sec^?1 with high lithium deficit, and increases markedly when approaching ideal stoichiometry. The activation energies are small, 0.1–0.3 eV, depending on the stoichiometry, in both phases. The mobility of lithium in “Li₃Bi” is about 500 times greater than in “Li₃Sb” with a lithium deficit. The ionic conductivity in “Li₃Sb” increases from about 10^?4 Ω^?1 cm^?1 in the vacancy transport region to about 2 × 10^?3 where transport is probably by interstial motion at 360°C. For “Li₃Bi” a practically constant value of nearly 10^?1 Ω^?1 cm^?1 is found at 380°C. The parabolic tarnishing rate constant shows a sharp increase at higher lithium activities in “Li₃Sb” whereas in “Li₃Bi” it has a roughly linear dependence upon the logarithm of the lithium activity. The tarnishing process is about 2 orders of magnitude slower for “Li₃Sb” than for “Li₃Bi.” Because of the fast ionic transport in these mixed conducting materials, “Li₃Sb” and “Li₃Bi” may be called “fast electrodes.”     

Analysis of linear free-energy relationships combined with activation parameters assigns a concerted mechanism to alkaline hydrolysis of x-substituted phenyl diphenylphosphinates

A kinetic study is reported for alkaline hydrolysis of X‐substituted phenyl diphenylphosphinates ( 1 a – i ). The Brønsted‐type plot for the reactions of 1 a – i is linear over 4.5 pK_a units with β_lg=?0.49, a typical β_lg value for reactions which proceed through a concerted mechanism. The Hammett plots correlated with σ^o and σ^? constants are linear but exhibit many scattered points, while the corresponding Yukawa–Tsuno plot results in excellent linear correlation with ρ=1.42 and r=0.35. The r value of 0.35 implies that leaving‐group departure is partially advanced at the rate‐determining step (RDS). A stepwise mechanism, in which departure of the leaving group from an addition intermediate occurs in the RDS, is excluded since the incoming HO^? ion is much more basic and a poorer nucleofuge than the leaving aryloxide. A dissociative (D_N + A_N) mechanism is also ruled out on the basis of the small β_lg value. As the substituent X in the leaving group changes from H to 4‐NO₂ and 3,4‐(NO₂)₂, ΔH ^≠ decreases from 11.3 kcal mol^?1 to 9.7 and 8.7 kcal mol^?1, respectively, while ΔS ^≠ varies from ?22.6 cal mol^?1 K^?1 to ?21.4 and ?20.2 cal mol^?1 K^?1, respectively. Analysis of LFERs combined with the activation parameters assigns a concerted mechanism to the current alkaline hydrolysis of 1 a – i .     

(Nitronyl Nitroxide)‐Substituted Trioxytriphenylamine Radical Cation Tetrachlorogallate Salt: A 2p‐Electron‐Based Weak Ferromagnet Composed of a Triplet Diradical Cation

The synthesis and the solid state magnetic properties of (nitronyl nitroxide)‐substituted trioxytriphenylamine radical cation tetrachlorogallate, NNTOT+·GaCl4? , are reported. In the temperature region between 300 and 3 K, the magnetic behavior is characterized by the strong intramolecular ferromagnetic interaction (J/k_B=+400 K) between the radical ( NN ) and the radical cation ( TOT ⁺) and the weak intermolecular antiferromagnetic interaction (J/k_B=?1.9 K) between NNTOT⁺ ions. Below 3 K, a 3D‐type long‐range magnetic ordering into a weak ferromagnet was observed (T_N=2.65 K). The magnetic entropy (S_mag=8.97 J K^?1 mol^?1) obtained by the heat capacity measurement is in good agreement with the theoretical value of R ln3=9.13 J K^?1 mol^?1 based on the S=1 state.     

Mannose‐based graft polyesters with tunable binding affinity to concanavalin A

Glycopolymers have been widely used to understand the interactions between carbohydrates and lectins, which facilitate the diagnosis and detection of disease and pathogens as well as the development of vaccines. While studies have been focused on the correlation of glycopolymer structure and their binding to lectins, graft‐type glycopolyesters are uncommon. Herein, we report the design and synthesis of mannose‐based graft polyesters by “grafting‐from” method and investigate their interactions with Concanavalin A (Con A). As confirmed by ¹H NMR spectroscopy and sulfuric acid‐UV method, graft polyesters with different lengths of mannose graft were successfully synthesized. Our results from turbidimetry binding assay showed that graft polyesters with longer mannose graft exhibit higher initial binding rate (k_i). Isothermal titration calorimetry measurements of these graft polyesters with Con A showed that polymers exhibit higher binding affinity (k_a) with the number of side chain mannose. This study provides understanding of the interaction between Con A and mannose‐based graft polyesters, which can be employed for the development of glycopolymeric therapeutics. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 3908–3917     

The Employ of Multiple Voltammetric Pulses for the Study of the Adsorption of Bipyridilium Pesticides in River Sediment

The multiple square‐wave voltammetry (MSWV) allied to gold microelectrode (Au‐ME) was used to establish an electroanalytical procedure for the determination of the paraquat and diquat pesticides in river sediment samples. For both pesticides, two reduction peaks, at around ?0.70 V (peak 1) and around ?1.00 V vs. Ag/AgCl 3.00 mol L^?1 (peak 2), with profile of the totally reversible redox process, were observed. The experimental and voltammetric conditions showed that the best conditions to reduce paraquat and diquat were a pH of 6.0, a frequency of 250 s^?1, a scan increment 2 mV, a square‐wave amplitude of 50 mV and pulse number of 8 pulses of potential in each step of staircase of potential. Under such conditions, the detection limit of 0.044 μg L^?1 (0.044 ppb) and 0.360 μg L^?1 (0.360 ppb ) for peak 1 and peak 2 of paraquat and 0.159 μg L^?1 (0.159 ppb) and 0.533 μg L^?1 (0.533 ppb) for peak 1 and peak 2 of diquat, respectively, were obtained. These results are an order of magnitude of about two less than those obtained and published in the literature. Also, the electroanalytical procedure proposed was applied for the determination of adsorption isotherms of pesticides on river sediments samples collected from Mogi‐Guaçu River in Sao Paulo State, Brazil. The experimental data were fitted using the Langmuir and Freundlich isotherms models; and the results indicated low intensities of adsorption process of the pesticides in the samples employed with distribution coefficients (K_d) lower 5.0, and paraquat showed slightly higher affinity than diquat in the sediments. The increase in organic matter and organic carbon leads to an increase in the K_d values, and consequently an increase in the organic matter constant (K_OM) organic carbon constant (K_OC) values. All results demonstrated that isotherms “L” type in the Giles classification were obtained, indicating that sediments have a medium affinity for the pesticides, and no strong competition from the solvent used (in this case Na₂SO₄) for adsorption sites occurs.     

Iridium(III) Complexes Bearing Pyrene‐Functionalized 1,10‐Phenanthroline Ligands as Highly Efficient Sensitizers for Triplet–Triplet Annihilation Upconversion

“Chemistry‐on‐the‐complex” synthetic methods have allowed the selective addition of 1‐ethynylpyrene appendages to the 3‐, 5‐, 3,8‐ and 5,6‐positions of Ir^III‐coordinated 1,10‐phenanthroline via Sonogashira cross‐coupling. The resulting suite of complexes has given rise to the first rationalization of their absorption and emission properties as a function of the number and position of the pyrene moieties. Strong absorption in the visible region (e.g. 3,8‐substituted Ir‐3 : λ_abs=481 nm, ?=52 400 m ^?1 cm^?1) and long‐lived triplet excited states (e.g. 5‐substituted Ir‐2 : τ_T=367.7 μs) were observed for the complexes in deaerated CH₂Cl₂. On testing the series as triplet sensitizers for triplet–triplet annihilation upconversion, those Ir^III complexes bearing pyrenyl appendages at the 3‐ and 3,8‐positions ( Ir‐1 , Ir‐3 ) were found to give optimal upconversion quantum yields (30.2 % and 31.6 % respectively).     

Spectroscopic investigations of hematoxylin–Eu(III) complex interacting with Herring-sperm DNA

The interaction of HE–Eu(III) complex (HE?=?hematoxylin) with Herring-sperm DNA (hsDNA) has been studied by absorption spectra, fluorescence, and viscosity measurements in physiological buffer (pH?=?7.40). The binding constant of HE–Eu(III) complex to hsDNA was obtained by double reciprocal method at 298 and 310?K and the corresponding thermodynamic parameters (Δ_r Hm??=?8.55?×?10⁴?J?mol^?1, Δ_r Gm??=??3.01?×?10⁴?J?mol^?1, Δ_r Sm??=?387.95?J?mol^?1?K^?1) were calculated, showing that the interaction between HE–Eu(III) complex and hsDNA was driven mainly by entropy. The value of K indicated that the binding mode of HE–Eu(III) complex with DNA was not classical intercalation. These results were further supported by viscosity method and competitive binding experiment. Scatchard analysis suggests that the interaction mode was a mixed binding, which contains partial intercalation and groove binding.