Spectroscopy Titration Research Articles

Synthesis and Fluorescent Sensing Properties for Ce3+ Ions of Di-Schiff Base Amine Containing Amaide Bridge Probe

A fluorescent probe (L) of di-Schiff base amine ligand was designed and synthesized from 2,6-pyridine-dicarboxylic acid, ethylenediamine and p-hydroxybenzaldehyde by condensation reaction and reduction reaction. The structure was confirmed by means of IR, UV, 1H NMR and MS. The research of fluorescence spectroscopy indicated that the probe L exhibited high selectivity for Ce3+. The spectroscopic titration indicated that A good linear work curve with R2 = 0.99607, the stoichiometry of the Ce3+ complex was 1:1, the minimum detection limits for Ce3+was 3.8382×10-6 mol/L and the binding constant of L to Ce3+ was estimated as 6.3734×107 (mol/L)-1. It was expected to be applied to the detection of trace Ce3+.

Investigation of Chloride Anion Binding Properties of Glipizide Drug

This study addresses the anion binding property of Glipizide (GLP), an oral antidiabetic a second-generation drug member of the sulphonylurea (SU) family. GLP effectively interacts with Cl- anion according to 1H-NMR spectroscopic titrations of successive tetrabutylammonium chloride (TBACl) in deuterated chloroform (CDCl3) and dimethyl sulfoxide (d6-DMSO). Upon the addition of TBACl, the change in chemical shift was observed for both N-H protons of SU in CDCl3, whereas it causes a difference in the shift of only one of N-H proton in SU in d6-DMSO. In addition, the data obtained from 1H-NMR spectroscopic titrations was analyzed by DynaFit program to calculate the binding constant (Ka) value between GLP and Cl- anion. It was found that GLP binds Cl- anion in CDCl3 with higher affinity (Ka=77.37 M-1, Fitplot for N-Hh proton at δ=6.47 ppm) than in d6-DMSO (Ka=38.53 M-1, Fitplot for N-Hh proton at δ=6.32 ppm).

Inclusion Complexes of a Metastable‐State Photoacid with High Acidity and Chemical Stability

AbstractMetastable‐state merocyanine photoacids (MCHs) have been widely applied to various chemical, material and biomedical areas to drive or control chemical processes with light. In this work, stoichiometry and association constants have been determined for inclusion complexes of a photoacid MCH1 ((E)‐3‐(2‐(2‐hydroxystyryl)‐3,3‐dimethyl‐3H‐indol‐1‐ium‐1‐yl)propane‐1‐sulfonate) with β‐cyclodextrin (β‐CD), 2‐hydroxypropyl‐β‐CD (HP‐β‐CD), γ‐CD and HP‐γ‐CD by means of UV‐Vis absorption spectroscopic titrations. The inclusion complexes were studied to enhance acidity and chemical stability. Kinetic study showed that CDs stabilized the acidic metastable state and slowed its thermal relaxation. The acidity of the ground and metastable state (pKaGS and pKaMS) increased upon addition of CDs. The pKaMS of [MCH1 ⋅ (γ‐CD)2] is as low as 0.92 in comparison with 2.24 for MCH1, which is close to the lowest pKaMS values (1.20 and 1.03) reported previously, in which case the MCH1 was structurally modified with alkylammonium side chains. Addition of CDs also significantly enhanced the chemical stability of MCH1 against hydrolysis, which is one of the major concerns for the application of MCHs. In particular, the addition of HP‐β‐CD increased the half‐life of MCH1 in aqueous solution more than four‐fold. Moreover, the quantum chemical calculations confirmed the stoichiometry and analyzed the binding sites and hydrogen bonds of the inclusion complexes.

High-Throughput Lithium Plating Quantification for Fast Charging Battery Design

Fast charging of most commercial lithium-ion batteries is limited due to fear of lithium plating on the graphite anode, which is difficult to detect and poses significant safety risk. Here we demonstrate the power of simple, accessible, and high-throughput cycling techniques to quantify irreversible Li plating spanning data from over 100 cells. We first demonstrate a protocol for Li|Graphite half-cells to observe the effects of energy density, charge rate, temperature, and State-of-Charge (SOC) on lithium plating and provide an interpretable empirical equation for predicting the plating onset SOC. We then design a method to quantify in-situ Li plating for commercially relevant Graphite|LiNi0.5Mn0.3Co0.2O2 (NMC) cells and compare with results from the experimentally convenient Li|Graphite configuration. Ex-situ mass spectrometry titration is used to validate the in-situ analysis methods. This work showcases innovative testing methods and data processing that enable rapid battery engineering.

Platinum (II) complex of isopentyl glycine ligand: DNA binding, molecular dynamic, and anticancer activity against breast cancer

In this paper, we performed thorough experimental and theoretical calculations to examine the interaction between Pt derivative, as an anticancer, and ct-DNA. The mode of DNA binding with [Pt(NH3)2(Isopentylgly)]NO3, where Isopentylgly is Isopentyl glycine, was evaluated by various spectroscopic methods, docking, and molecular dynamics simulation studies. UV-Vis and fluorescence spectroscopic titration results and CD spectra of DNA-drug showed this interaction is via groove binding. Also, thermal stability studies or DNA melting temperature changes (ΔTm), as well as the quenching emissions monitoring proved it. Also, the thermodynamic parameter and binding constant displayed that complex-DNA formation is a spontaneous process, and H-binding and also groove binding were found to be the main forces. Theoretical studies stated [Pt(NH3)2(Isopentylgly)]NO3-DNA formation occurs on C-G center on DNA, along with rising DNA-compound stability. IC50 value against the human breast cell line probably is due to the Isopentyl glycine ligand in the structure of the Pt compound, and it was obtained more than cisplatin and less than carboplatin against the MCF7 cell. Communicated by Ramaswamy H. Sarma

An oxazole-derived Schiff base as a multifunctional fluorescence sensor towards Al3+ and Ga3+ in different media

A facile Schiff base derivative N′-(2, 3-dihydroxybenzylidene)-5-(naphthalen-1-yl)oxazole-4-carbohydrazide (G3) was constructed and synthesized through the reaction of 5-(naphthalen-1-yl)oxazole-4-carbohydrazide with 2,3-dihydrobenzaldehyde, which achieved the distinct recognition for two kinds of IIIA group metal ions (Al3+, Ga3+) in different media. G3 performed an enhanced blue luminescence upon addition of Al3+ in CH3OH/H2O buffer solution. As well, G3 exhibited a remarkable fluorescence enhancement toward Ga3+ with a color change from colorless to green in DMSO/H2O buffer solution. Therefore, G3 was applied as a multifunctional fluorescence sensor for Al3+ and Ga3+. The molar ratio for G3 towards Al3+ and Ga3+ was both verified to be 1:2, and the possible sensing mechanism was demonstrated by Job's plot, mass spectrometry titration and theoretical calculation. What’ more, G3 could be used to determinate target ions in real water samples with favorable recovery, which implied a wide prospect for application. And more importantly, the fine difference on microstructure causing the macroscopic performance of sensors in the buffer solution was revealed through the contrastive study of G3 and G1 in previous work.

Interactions of arene ruthenium(II) complexes [η6-(C6H6)Ru(pprip)Cl]+ and [η6-(C6H6)Ru(H2iiP)Cl]+ with RNA triplex poly(U)•poly(A)*poly(U).

Two arene ruthenium(II) complexes [η6-(C6H6)Ru(pprip)Cl]PF6 (Ru1; pprip = 2-(3-phenyl-1H-pyrazol-4-yl)-imidazolo[4,5-f][1,10]phenanthroline) and [η6-(C6H6)Ru(H2iiP)Cl]PF6 (Ru2; H2iiP = 2-(indole-3-yl)-imidazolo[4,5-f][1,10]phenanthroline) have been synthesized and characterized in this work. Binding properties of Ru1 and Ru2 with the triplex RNA poly(U)•poly(A)*poly(U) were investigated by spectrophotometry and spectrofluorometry as well as viscosimetry. Analysis of spectroscopic titrations and viscosity measurements show that the two complexes bind with the triplex through intercalation, while the binding affinity for Ru2 toward the triplex is stronger than that for Ru1. Melting experiments indicate that the stabilizing effects of Ru1 and Ru2 toward the triplex differ from each other. Under the conditions used herein, Ru1 only stabilizes the Hoogsteen base-paired strand (third strand) without affecting stabilization of the Watson-Crick base-paired strand (the template duplex) of the triplex, while Ru2 stabilizes both the template duplex and the third strand. Although the two complexes prefer to stabilizing the third strand rather than the template duplex, the third-strand stabilization effect of Ru2 is stronger than that of Ru1. The obtained results of this work reveal that the planarity of the intercalative ligands plays an important role in the triplex stabilization by arene Ru(II) complexes.

Compounds Derived from 9,9‐Dialkylfluorenes: Syntheses, Crystal Structures and Initial Binding Studies (Part II)

AbstractNew representatives of 2,4,7‐trisubstituted 9,9‐dialkyl‐9H‐fluorenes were prepared and used for crystallographic investigations as well as initial binding studies towards metal ions and carbohydrates. The binding studies, which included 1H NMR spectroscopic titrations and fluorescence measurements, demonstrated the ability of the tested fluorene‐based compounds to act as complexing agents for ionic and neutral substrates. Depending on the nature of the subunits of the fluorene derivatives, “turn on” or “turn off” fluorescent chemosensors can be developed. Compounds composed of 4,6‐dimethylpyridin‐2‐yl‐aminomethyl moieties have the potential to be used as sensitive “turn‐on” chemosensors for some metal ions.

Exploring DNA-interaction and molecular structure of ruthenium/1,2-bis-(diphenylphosphino)ethane)-based complex

The mixture of cis and trans-[RuCl2(dppe)2] (dppe: 1,2-bis-(diphenylphosphino)ethane) was prepared and the interaction with CT-DNA was evaluated by several methods, including UV-vis DNA spectroscopic titration, viscosity, and electrochemical studies. Investigation suggests that [RuCl2(dppe)2] interacts moderately with CT-DNA. Interestingly, the cis- and trans-isomers interact differently with DNA, as proved by the square-wave voltammetry studies. Finally, the crystal structure of trans-[RuCl2(dppe)2]Cl was obtained from an electrochemical solution and studied in detail, which presents a distorted octahedral geometry and interatomic parameters different from those found in the trans-[RuCl2(dppe)2] complex. Crystal data for C52H48Cl4P4Ru: triclinic, space group P-1 (no. 2), a = 9.240(3) Å, b = 10.9290(18) Å, c = 11.993(3) Å, α = 78.707(11)°, β = 86.712(13)°, γ = 82.598(13)°, V = 1177.1(5) Å3, Z = 1, T = 293(2) K, μ(MoKα) = 0.732 mm-1, Dcalc = 1.467 g/cm3, 8434 reflections measured (6.934° ≤ 2Θ ≤ 51.986°), 4607 unique (Rint = 0.0973, Rsigma = 0.1171) which were used in all calculations. The final R1 was 0.0537 (I > 2σ(I)) and wR2 was 0.1347 (all data).

Eu(III) and Cm(III) Complexation by the Aminocarboxylates NTA, EDTA, and EGTA Studied with NMR, TRLFS, and ITC-An Improved Approach to More Robust Thermodynamics.

The complex formation of Eu(III) and Cm(III) was studied via tetradentate, hexadentate, and octadentate coordinating ligands of the aminopolycarboxylate family, viz., nitrilotriacetate (NTA3-), ethylenediaminetetraacetate (EDTA4-), and ethylene glycol-bis(2-aminoethyl ether)-N,N,N',N'-tetraacetate (EGTA4-), respectively. Based on the complexones' pKa values obtained from 1H nuclear magnetic resonance (NMR) spectroscopic pH titration, complex formation constants were determined by means of the parallel-factor-analysis-assisted evaluation of Eu(III) and Cm(III) time-resolved laser-induced fluorescence spectroscopy (TRLFS). This was complemented by isothermal titration calorimetry (ITC), providing the enthalpy and entropy of the complex formation. This allowed us to obtain genuine species along with their molecular structures and corresponding reliable thermodynamic data. The three investigated complexones formed 1:1 complexes with both Eu(III) and Cm(III). Besides the established Eu(III)-NTA 1:1 and 1:2 complexes, we observed, for the first time, the existence of a Eu(III)-NTA 2:2 complex of millimolar metal and ligand concentrations. Demonstrated for thermodynamic studies on Eu(III) and Cm(III) interaction with complexones, the utilized approach is commonly applicable to many other metal-ligand systems, even to high-affinity ligands.

Terpyridine-Zn(II) based water-soluble fluorescent probes for selective detection of pyrophosphate ions in aqueous medium and its bioimaging application in living cells

Pyrophosphate (PPi) is a key biomarker for various cellular processes and human diseases and thus the development of receptors to bind selectively with PPi ions and facilitate the monitoring of intracellular PPi concentration in living cells is highly imperative. In the present study, novel water-soluble terpyridine-Zn(II) complexes-based fluorescent probes [TPD-Zn2]Cl4 and [TPTBr-Zn2]Cl4 have been designed and synthesized for the selective and sensitive detection of pyrophosphate (PPi) ions in aqueous environment as well as in living cells. The selectivity investigations of both the fluorescent probes towards different anions in HEPES buffer (pH = 7.4) showed highly selective binding towards PPi ions even in the presence of other concomitant nucleotides. Both the probes [TPD-Zn2]Cl4 and [TPTBr-Zn2]Cl4 have exhibited linear fluorescence enhancement upon the addition of different concentrations of PPi and this enhancement in the intensity could be attributed to the photoinduced electron transfer (PET) inhibition process. This proposed binding mechanism was demonstrated using fluorescence and NMR spectroscopic titrations and also the interaction of [TPD-Zn2]Cl4 and [TPTBr-Zn2]Cl4 probes with PPi ions was examined in detail using density functional theory (DFT) analysis. The Job’s plot has shown the binding of complexes between [TPD-Zn2]Cl4 and [TPTBr-Zn2]Cl4 and PPi in 1:2 stoichiometry and the probes have shown excellent binding affinity towards PPi ions with binding constants of 7.72 × 105 M−2 and 6.74 × 104 M−2, respectively. Noticeably, both the probes exhibited promising sensitivity towards PPi with detection limits as low as 0.47 nM and 0.17 nM, respectively. Cytotoxicity studies of [TPD-Zn2]Cl4 and [TPTBr-Zn2]Cl4 revealed that both the probes are biocompatible and subsequently their diagnostic efficacy as bioimaging probes was demonstrated through monitoring the intracellular PPi concentrations in breast cancer cells (MCF-7).

Dynamic Metalloporphyrin-Based [2]Rotaxane Molecular Shuttles Stimulated by Neutral Lewis Base and Anion Coordination.

A series of dynamic metalloporphyrin [2]rotaxane molecular shuttles comprising of bis-functionalised Zn(II) porphyrin axle and pyridyl functionalised macrocycle components are prepared in high yield via active metal template synthetic methodology. Extensive variable temperature 1 H NMR and quantitative UV-Vis spectroscopic titration studies demonstrate dynamic macrocycle translocation is governed by an inter-component co-ordination interaction between the macrocycle pyridyl and axle Zn(II) metalloporphyrin, which serves to bias a 'resting state' co-conformation. The dynamic shuttling behaviour of the interlocked structures is dramatically inhibited by the addition of a neutral Lewis base such as pyridine, but can also be tuned via post-synthetic rotaxane demetallation of the porphyrin axle core to give free-base, or upon subsequent metallation, Ni(II) [2]rotaxane analogues. Importantly, the Lewis acidic Zn(II) porphyrin axle component is also capable of coordinating anions which induces mechanical bond shuttling behaviour resulting in a novel optical sensing response.

Copper(II)/diiminic complexes based on 2-hydroxybenzophenones: DNA- and BSA-binding studies and antitumor activity against HCT116 and HepG2 tumor cells

Here, we report four new heteroleptic Cu(II) complexes with the formula [Cu(bipy)(2H4MeBz)]NO3 (1), [Cu(phen)(2H4MeBz)]NO3 (2), [Cu(bipy)(2H4OcBz)]NO3 (3) and [Cu(phen)(2H4OcBz)]NO3 (4), where the ligands are 2-hydroxy-4-methoxybenzophenone (2H4MeBz), 2-hydroxy-4-(octyloxy)benzophenone (2H4OcBz), 2,2′-bipiridine (bipy) and 1,10-phenantroline (phen). All compounds present two bidentate ligands, a monoanionic 2-hydroxybenzophenone, forming a six-membered chelate ring and the diiminic ring forming a five-membered chelate ring, as well as one nitrate as counterion located at the axial position, as suggested by the crystal structure of complex 2. Complex/DNA interaction studies were also performed using spectroscopic titration (Kb close to 104 M−1), viscosity, Hoechst 33258 competition, and circular dichroism, revealing a moderate interaction between them. Additionally, complexes 1–4 moderately interact with BSA (Bovine Serum Albumin). The compounds were evaluated against HCT116 (human colon carcinoma) and HepG2 (human hepatocellular carcinoma) cancer cells and against MRC-5 (human lung fibroblast), a noncancer cells. The cytotoxic results suggest that complexes 2 and 4 are more cytotoxic than 1 and 3, showing that the presence of phen ligand may play an important role in increasing the biological effect of the compounds.

A fluorescent receptor for alkylammonium ions based on an anthryl-linked triazole-modified hexahomotrioxacalix[3]arene

A novel C3-symmetrical anthracene-functionalized hexahomotrioxacalix[3]arene L was synthesized via Click chemistry and its chemosensing properties with alkylammonium ions were investigated. The significant fluorescence enhancements were observed with addition of alkylammonium ions (including primary and tertiary ones), indicating a high selectivity for alkylammonium ions. Our studies demonstrated that the detection limit on fluorescence response of the sensor to is in the 10–6 M range. The mechanism of the interaction between the L and alkylammonium ions has been investigated in detail by 1H NMR spectroscopic titration experiments. Density functional theory (DFT) quantum chemical calculations were conducted to estimate the electronic interaction energies (ΔIE) between the chemosensor L and alkylammonium ions.

Interaction of water soluble phthalocyanine compounds with parallel and hybrid G-quadruplex DNA molecules

G-quadruplex DNAs are secondary DNA structures formed in guanine-rich genome sequences, such as telomeres. Due to the increased metabolic activities of cancer cells, the formation probability of G-quadruplex structures increases. Since the formation of G-quadruplex structures and their stabilization with various ligands prevents DNA’s turning into straight strands, which are necessary for some processes such as transcription and translation, it may cause disruptions in cell proliferation. Therefore, these DNA constructs are important for anticancer drug targets. In the present study, the interactions of water-soluble MnPc and ZnPc compounds with G-quadruplex DNAs with parallel and hybrid conformation were investigated. KD constants were calculated with spectroscopic titration data. Stoichiometric ratios of DNA-phthalocyanine interactions were determined by Job’s method and found between 1:1 to 1:2 for MnPc and 1:1 for ZnPc. The effect of phthalocyanine on the G-quadruplex conformation was investigated by circular dichroism (CD) spectroscopy. Capillary gel electrophoresis studies supported the existence of interactions. DNA polymerase stop assay further supported stabilizing AS1411 and Tel21 G-quadruplex structures with Pc compounds. This work is on a molecular level study. The in vitro and in vivo images can be different because MPcs are localized in the cytoplasmic organelles but rare in the nucleus.

A Rhodamine B-Salicylic Acid Compound with Colorimetric /Fluorescent Dual Channel Response for the Identification of Fe3+

In this paper, a rhodamine B-salicylic acid based binary compound probe RB-SA was designed and synthesized, and its structure was characterized by 1HNMR and 13CNMR. The probe provides a colorimetric/fluorescent dual-channel response to Fe3+ in the aqueous phase. Under the induction of Fe3+, the spirolactam ring of the probe RB-SA changed from closed loop to open loop, and a new absorption peak appeared at 560 nm and the solution color changed from colorless to red, while the fluorescence signal turned on, and the fluorescence intensity at 587 nm increased linearly with the addition of Fe3+. It was shown that the probe RB-SA exhibited high sensitivity to Fe3+, with a minimum detection limit (LOD) of 5.19 nM and a complexation constant of 1.03 × 104 M-1 based on fluorescence spectroscopy titration data.

Synthesis and characterization of N4-substituted thiosemicarbazones: DNA/BSA binding, molecular docking, anticancer activity, ADME study and computational investigations

A series of thiosemicarbazones with the general formula, R−CHN−NH−C(S)−R1 [R = C6H5F & R1= C4H9NO (TL1), R = C8H10O2 & R1= C4H9NO (TL2), R = C6H5F & R1= C4H9N (TL3), R = C6H5Br & R1= C4H9N (TL4)] were synthesized. The UV–Visible, Infra-red, NMR and HRMS spectra were used to confirm compounds. The single-crystal X-ray diffraction (XRD) technique was used to determine the molecular composition of TL3 and TL4. Absorption/emission spectroscopic titrations were subjected to evaluate the compounds' interactions with Calf-Thymus (CT) DNA. According to DNA binding research findings, the compounds were bound to DNA in an interactive manner, as evidenced by the hypochromic and slight red shift. The compound TL3 possesses a high binding constant (5.17 × 106 M−1), which indicates that it bound CT-DNA more firmly than other compounds. The red shift and strong hypochromic shift observed in the fluorescence titration spectrum of BSA binding studies described a strong interaction of compounds with BSA. The compound TL3 exhibits a redshift of 3 nm and 92% quenching. The BSA protein docking studies of the compounds revealed their ability to act as medicines for the targets. Amongst the four compounds, TL3 shows high binding energy towards BSA ( ̶ 6.33 Kcal/mol) protein. B3LYP/ 6–311 G (d, p) level theories were used to compute density functional theory (DFT). Computational evaluations of the generated compounds show that the compound TL2 has significantly higher structural stability than other compounds. According to SwissADME studies, the LogP values for all compounds were less than 5, indicating appropriate lipophilicity characteristics. The low degree of synthetic accessibility ranges from 2–3, indicating a quality result for this characteristic. In other words, all the compounds TL1-TL4 have the potential to evolve into good oral drug candidates. Anticancer activity of four compounds (TL1-TL4) was investigated on human HepG-2-liver, EAhy-926-endothelial carcinoma cancer and African green monkey normal Vero cells. The compound TL3 showed good activity in liver and endothelial carcinoma cancer cells with IC50 values of 37.5 and 30.1 µM, respectively.

Selective Complexation and Separation of Uranium(VI) from Thorium(IV) with New Tetradentate N,O-Hybrid Diamide Ligands: Synthesis, Extraction, Spectroscopy, and Crystallographic Studies.

An unmet challenge in the thorium-uranium fuel cycle is the efficient separation of uranium from thorium. Herein, two new tetradentate N,O-hybrid ligands, N,N'-diethyl-N,N'-di-p-tolyl-2,2'-bipyridine-6,6'-dicarboxamide (Et-Tol-BPDA) and N,N'-diethyl-N,N'-di-p-tolyl-2,2'-bipyrimidine-4,4'-dicarboxamide (Et-Tol-BPymDA), comprising a bipyridine or bipyrimidine core and amide moieties were designed and synthesized for selectively complexing and separating U(VI) from Th(IV). The high U(VI)/Th(IV) extraction selectivity was achieved by Et-Tol-BPDA (SFU/Th = 33 at 3 M HNO3) and Et-Tol-BPymDA (SFU/Th = 73 at 3 M HNO3) in nitric acid solutions. The extraction process for U(VI) or Th(IV) with these two ligands primarily proceeded through the solvation mechanism, as evidenced by slope analyses. Thermodynamic studies for the extraction of U(VI) and Th(IV) revealed a spontaneous process. Results from UV-vis spectroscopic titration and slope analyses demonstrated that U(VI) and Th(IV) each form a 1:1 complex with the two ligands both in the monophasic organic solution and the biphasic extraction system. The stability constants of the 1:1 complexes of Et-Tol-BPDA or Et-Tol-BPymDA with U(VI) were found to be larger than those with Th(IV), which coincide well with the high U(VI)/Th(IV) extraction selectivity. The solid-state structures of Et-Tol-BPDA, Et-Tol-BPymDA, and 1:1 complexes of the two ligands with U(VI) or Th(IV) were analyzed by X-ray diffraction technique. The results from this work implicate the potential of bipyridine- and bipyrimidine-derived diamide ligands for uranium/thorium separation.

Exploring a new family of designer copper(II) complexes of anthracene-appended polyfunctional organic assembly displaying potential anticancer activity via cytochrome c mediated mitochondrial apoptotic pathway

The present article describes the systematic study on design and synthesis, physicochemical properties and spectroscopic features, and potential anticancer activities of a family of novel copper(II)-based designer metal complexes [Cu2(acdp)(μ-Cl)(H2O)2] (1), [Cu2(acdp)(μ-NO3)(H2O)2] (2) and [Cu2(acdp)(μ-O2CCF3)(H2O)2] (3) of anthracene-appended polyfunctional organic assembly, H3acdp (H3acdp = N,N′-bis[anthracene-2-ylmethyl]-N,N′-bis[carboxymethyl]-1,3-diaminopropan-2-ol). Synthesis of 1–3 was accomplished under facile experimental conditions, preserving their overall integrity in solution. The incorporation of polycyclic anthracene skeleton within the backbone of organic assembly increases lipophilicity of resulting complexes, thereby dictating the degree of cellular uptake with improved biological activity. Complexes 1–3 were characterized by elemental analysis, molar conductance, FTIR, UV–Vis absorption/fluorescence emission titration spectroscopy, PXRD and TGA/DTA studies, including DFT calculations. The cellular cytotoxicity of 1–3 when studied in HepG2 cancer cell line showed substantial cytotoxic effects, whereas no such cytotoxicity was observed when exposed to normal L6 skeletal muscle cell line. Thereafter, the signaling factors involved in the process of cytotoxicity in HepG2 cancer cells were investigated. Alteration of cytochrome c and Bcl-2 protein expression levels along with modulation of mitochondrial membrane potential (MMP) in the presence of 1–3, strongly suggested the possibility of activating mitochondria-mediated apoptotic pathway involved in halting the cancer cell propagation. However, when a comparative assessment on their bio-efficacies was made, 1 showed higher cytotoxicity, nuclear condensation, DNA binding and damage, ROS generation and lower rate of cell proliferation compared to 2 and 3 in HepG2 cell line, indicating that the anticancer activity of 1 is significantly higher than that of 2 and 3.

Anion Modulated Expression of Chirality in Hydrogen Bond Templated Mechanically Chiral [2]Rotaxanes.

The syntheses of two novel mechanically chiral rotaxanes containing urea and squaramide motifs (in yields of 33 % and 22 %, respectively) are presented. 1 H NMR spectroscopic titrations reveal shuttling of the macrocycle - detectable by modulation of the expression of mechanical chirality in the NMR spectrum - is possible through the addition of achiral chloride anions, a process which is reversed by the addition of sodium cations.