Peripheral Carboxyl Research Articles

Sustainable synthesis of chromene derivatives catalysed by magnetite nanoparticle cored polyamine dendrimer

Chromene derivatives are naturally occurring heterocyclic compounds used as cosmetic agents, food additives, and potential biodegradable agrochemicals. Normally, its synthesis is carried out with three component/substrates with a suitable base. Dendrimer with amine functionality has several applications in catalysis, more specifically, dendrimers having enriched amino groups with accessible void makes a significant impact in base catalysis. Moreover, polar periphery of the dendrimers may enhance the solubility of material in the reaction medium. Therefore, herein we report the base catalytic efficiency of magnetite nanoparticle supported polyamine dendrimer with enriched amine groups and peripheral carboxyl groups. Actually, magnetite supported polyamine dendrimer synthesis involves the synthesis of PAMAM G3 on magnetite nanoparticle core, followed by reduction of amide group with subsequent functionalization of carboxylic acid terminals. Further, it is used as versatile polyvalent base for the synthesis of chromene derivatives. The magnetite supported dendritic scaffold has accessible voids and polar periphery which enables them dispersible in the reaction medium. The recycle efficiency study confirms, the competency of the material to work in industrial catalysis.

Knocking the Stability of Solar Cells with Fluorescent Protein Donors upon Rationalizing Design, Integration, and Mechanism

AbstractThough photon‐induced electron donor features of fluorescent proteins (FPs) in solution suggest them as excellent photosensitizers, their poor stability upon device fabrication/operation is the today's frontier. This relates to their immediate denaturation in water‐free/less environments: inorganic/organic device interfaces and/or organic solvent surroundings. This study provides a fresh solution with a family of hybrid FPs, in which the peripheral carboxylic groups of archetypal FPs ‐superfolder green fluorescent protein (sfGFP) and mCherry‐ are transformed into alkoxysilane groups, enabling a straightforward integration with surprising stabilities over months in devices – arbitrary n/p‐type semiconducting metal oxide/FP/organic‐solvent electrolyte interfaces – attributed to the formation of an ion‐silica shell around the FP. This further allowed to understand the charge injection mechanism applying steady‐state/time‐resolved spectroscopy on different FP‐variants with key single‐point aromatic amino acid mutations at the chromophore nearest, revealing the electron‐donor hopping pathway via the initial loop of the strand β7. Finally, devices with state‐of‐the‐art solar‐to‐energy conversion efficiencies that are stable >2,000 h under operation nicely outperform the prior‐art stability of a few seconds/minutes in FP‐based solar cells. Hence, this work solves the integration/stability issues which blocking the application of FP‐based sensitizer, as well provides a solid understanding of their photo‐induced electron transfer mechanism.

Soluble Nanographene C222: Synthesis and Applications for Synergistic Photodynamic/Photothermal Therapy.

Nanographene C222, which consists of a planar graphenic plane containing 222 carbon atoms, holds the record as the largest planar nanographene synthesized to date. However, its complete insolubility makes the processing of C222 difficult. Here we addressed this issue by introducing peripheral substituents perpendicular to the graphene plane, effectively disrupting the interlayer stacking and endowing C222 with good solubility. We also found that the electron-withdrawing substituents played a crucial role in the cyclodehydrogenation process, converting the dendritic polyphenylene precursor to C222. After disrupting the interlayer stacking, the introduction of only a few peripheral carboxylic groups allowed C222 to dissolve in phosphate buffer saline, reaching a concentration of up to 0.5 mg/mL. Taking advantage of the good photosensitizing and photothermal properties of the inner C222 core, the resulting water-soluble C222 emerged as a single-component agent for both photothermal and photodynamic tumor therapy, exhibiting an impressive tumor inhibition rate of 96%.

Bis(4-carboxylpyrazol-1-yl)acetic acid: a scorpionate ligand for complexes with improved water solubility

Bis(4-carboxylpyrazol-1-yl)acetic acid (H3bcpza) (2), obtained in a one-pot synthesis, contains carboxyl groups that differ in their pKa values. The ligand exhibits heteroscorpionate κ3-N,N,O-coordination whereupon the peripheral carboxyl groups are not involved in metal binding. The corresponding carbonyl complexes [Mn(H2bcpza)(CO)3] (4), [Re(H2bcpza)(CO)3] (5) and [Ru(H2bcpza)Cl(CO)2] (6a/6b) are partially soluble in water but readily soluble in PBS buffer.

Nanogels and dendritic molecules combined to form a smart nanomaterial

Dendritic thermo-responsive polymer-based NGs were prepared following the precipitation methodology. PVCL-based dendritic NGs are reported with the incorporation of a dendritic building block, and with different percentages of N, N '-methylenebisacrylamide (BIS) as crosslinker agent. The dendritic moiety employed were di-tert-butyl-4-acryloylamine 4-[2-(tert-butoxy- carbonyl)ethyl]heptanodioate (ABA) and its hydrolyzed compound with peripheral carboxylic groups (ABC). In order to analyze the chemical structure, NGs were characterized using infrared microscopy. Hydrodynamic diameter and phase transition temperature were determined by dynamic light scattering. Phase transition temperature was also measured by UV–vis spectroscopy. Measures of electrophoretic mobility completed the characterization of the NGs. The phase transition temperature and Dh values were regulated by the percentage of crosslinker and the identity, quantity, steric effect, and polar character of the dendron.The polar and steric contributions of the dendritic block (ABA or ABC) were evidenced by the Dh, Tf and ζ values. For the P(VCL-co-ABC)-based dNGs, the hydrodynamic diameter was greater than the homopolymeric P(VCL) NGs, and even greater when the percentage of dendron increases, because of the hydrophilic periphery (acid groups). The presence of ABC allowed intramolecular hydrogen bonding due to the presence of the acid groups, and a decrease in the Tcp value by increasing the dendronization percentage was observed. The hydrogen bond intra- and intermolecular formations have a great impact on the conformation and surface properties.The detailed analysis of the property-structure relationship of the different NGs allowed us to prepare dNGs of nanometric size with a Tcp between 39 and 41 °C, which gives them potential applications in the biomedical area considering the average temperature of the human body.

Supramolecular Chirality from Hierarchical Self-Assembly of Atomically Precise Silver Nanoclusters Induced by Secondary Metal Coordination.

Chiral assembly of metal nanoparticles (NPs) into complex superstructures has been widely studied, but their formation mechanisms still remain mysterious due to the lack of precise structural information from the metal-organic interface to metallic kernel. As "molecular models" of metal NPs, atomically precise metal nanoclusters (NCs) used in the assembly of a macroscale superstructure will provide details of microscopic structure for deep understanding of such highly sophisticated assemblies; however, chiral superstructures have not been realized starting from achiral metal NCs with atomic precision. Herein, we report the supramolecular assembly of a water-soluble silver NC ((NH4)9[Ag9(mba)9], H2mba = 2-mercaptobenzoic acid, abbreviated as Ag9-NCs hereafter) into chiral hydrogels induced by the coordination of secondary metal ions. Single crystal X-ray diffraction reveals the triskelion-like structure of Ag9-NCs with a pseudochiral conformation caused by special arrangement of the peripheral mba2- ligands. The enantioselective orientation of the peripheral carboxyl group facilitates the assembly of Ag9-NCs into nanotubes with a chiral cubic (I*) lattice when coordinating to Ba2+. The nanotubes can further intertwine into one-dimensional chiral nanobraids with a preferred left-handed arrangement. These multiple levels of chirality can be tuned by drying, during which the I* phase is missing but the chiral entanglement of the nanotubes is enhanced. Through the gelation of atomically precise, achiral NCs coordination of secondary metal ions, chiral amplification of superstructures was realized. The origination of the chirality at different length scales was also discussed.

Synthetic modification of silica coated magnetite cored PAMAM dendrimer to enrich branched Amine groups and peripheral carboxyl groups for environmental remediation

Dendrimer with amine groups have several applications in gene delivery, drug delivery, metal encapsulation for catalysis and environmental remediation. Specifically, dendrimers having enriched amino groups with accessible void makes significant impact in the above fields. Besides, the carboxylic acid terminated amine dendrimers may enhance the efficacy as well. Therefore, herein we report the synthetic modification of poly(amidoamine) G3 dendrimer with magnetite core to enrich branched amine groups and peripheral carboxyl groups. To deliver this nanohybrid material, for the first-time silica coated magnetite cored poly(amidoamine) G3 dendrimer was synthesized by microwave assisted method. Subsequently amide groups present in the PAMAM have been reduced using lithium aluminum hydride to yield polyamine dendrimer namely poly (N-propylethane-1,2-diamine) G3. Further, peripheral amine groups were grafted with succinic anhydride to achieve carboxylic acid terminated dendrimer. The resulting nanomaterial was confirmed by FTIR, XRD, VSM, TGA, HRTEM and conductometry methods. In order to emphasize the structural efficacy of polyamine dendrimer, the metal ion uptake behavior has been discussed for the representative cations such as Pb2+, Cu 2+, Cr6+, Ca2+ and Ni2+ under the environmental concern. Magnetite cored polyamine dendrimer had evaluated for its recyclability test in the subsequent metal ion uptake studies and found to be satisfactory.

Interaction and Reactivity of Cisplatin Physisorbed on Graphene Oxide Nano-Prototypes.

The physical adsorption of cisplatin (CP) on graphene oxide (GO) and reduced graphene oxide (rGO) is investigated at the DFT level of theory by exploiting suitable molecular prototypes representing the most probable adsorbing regions of GO and rGO nano-structures. The results show that the CP binding energy is enhanced with respect to that for the interaction with pristine graphene. This is due to the preferential adsorption of the drug in correspondence of the epoxy and hydroxy groups located on GO basal plane: an energy decomposition analysis of the corresponding binding energy reveals that the most attractive contribution comes from the electrostatic attraction between the -NH ends of CP and the oxygen groups on (r)GO, which can be associated with hydrogen bonding effects. Moreover, it is found that the reactivity of the physically adsorbed CP is practically unaltered being the free energy variation of the first hydrolysis reaction almost matching that of its free (unadsorbed drug) counterpart. The reported results suggest that the CP physical adsorption on GO and rGO carriers is overall feasible being an exergonic process in aqueous solution. The CP adsorption could facilitate its solubility and transport in water solutions, exploiting the high hydrophilicity of the peripheral carboxylic groups located on the edge of the GO and rGO nano-structures. Moreover, the the higher affinity of CP with respect to the oxidized sites suggests a possible dependence of drug loading and release on pH conditions, which would highly facilitate its specific delivery.

Ru(II) porphyrins as sensitizers for DSSCs: Axial vs. peripheral carboxylate anchoring group

In this study, two porphyrin chromophores metallated with ruthenium, RuTBP and RuTBPPy, were prepared and studied as sensitizers in dye-sensitized solar cells (DSSCs). The difference between the two dyes is the position (axial vs. peripheral) of the carboxylic anchoring group. This work examines the impact of this variation towards the optical, electrochemical and photovoltaic performance of DSSCs. The thorough photophysical and photovoltaic measurements indicated that the peripherally substituted sensitizer (RuTBP) presented higher photovoltaic performance compared to RuTBPPy. More specifically, DSSCs sensitized with RuTBP and RuTBPPy displayed an overall power conversion efficiency (PCE) of 5.12% and 4.08%, respectively. The higher PCE value of the DSSC sensitized with RuTBP is mainly attributed to the enhancement of [Formula: see text] and FF values. These factors were enhanced due to the efficient dye regeneration process, the suppression of back-charge recombination reactions and the longer electron lifetimes as evidenced from the electrochemical impedance spectra.

Dendronized magnetic nanoparticles for HIV-1 capture and rapid diagnostic

Human immunodeficiency virus type 1 (HIV-1) remains a global public health problem. Detection and reduction of the rates of late diagnosis of HIV-1 infection are one of the main challenges in combating the HIV-1 epidemic. Magnetic nanoparticles (MNPs) have several characteristics that make them susceptible to capture HIV-1 of a wide range of biological samples reducing waiting times between the acquisition of HIV-1 infection and its detection by current techniques. Carbosilane dendrons decorated with peripheral carboxyl groups and alcoxysilane function at the focal point have been used to stabilize MNPs by co-precipitation method in one step. The characterization of these systems and of their carboxylate analogues was performed by Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), dynamic light scattering (DLS), ζ potential and thermal gravimetric analysis (TGA). The ability of carboxyl and carboxylate MNPs to capture R5-HIV-1 and X4-HIV-1 strains was evaluated to achieve a rapid and easy diagnostic method in order to reduce or eliminate the risk of HIV-1 transmission.

Inclusion of Peripheral Basic Groups Activates Dormant Cobalt-Based Molecular Complexes for Catalytic H2 Evolution in Water

The protein scaffold plays a key role during the enzymatic catalysis for metalloenzymes. Here we have rationally designed an enzyme-inspired outer coordination sphere in the form of protic functionalities, such as natural amino acid derived carboxylic acid and phenolic −OH groups, on the fringe of the cobalt-salen like complexes. This inclusion has enabled electrocatalytic H2 evolution for an otherwise inactive cobalt-salen like core. The complexes containing peripheral carboxylic acid groups exhibited unique pH-switchable catalytic H2 production that is connected with the pKa of the carboxylic acid group (∼4.0), suggesting the crucial involvement of the carboxylate group during the catalytic activity. The one- and two-dimensional NMR results of the complexes have indicated the presence of a possible hydrogen bonding network, generated by those protic groups in aqueous solution. These results highlight that an inactive metal complex can be activated for specific small molecule activation via rational incl...

Modulating the band gap and photoelectrochemical activity of dicarboxylate-stabilized titanium-oxo clusters

The dicarboxylate-stabilized titanium-oxo clusters (TOCs) [Ti6(μ3-O)4(μ2-OiPr)2(OiPr)8(BDC)2(O2CFc)2] (C1), [Ti6(μ3-O)4(μ2-OiPr)2(OiPr)8(TFBDC)2(O2CFc)2] (C2), and [Ti6(μ3-O)4(μ2-OiPr)2(OiPr)8(BDC)2(O2CC6H5)2] (C3) (BDC = 1,2-benzenedicarboxylate, TFBDC = 3,4,5,6-tetrafluoro-1,2-benzenedicarboxylate, Fc = ferrocenyl) were synthesized and structurally characterized. The band gap and photoelectrochemical (PEC) activity of the three Ti6-oxo clusters were effectively modulated by electronic effects of the peripheral carboxylate ligands. Moreover, with the same Ti6O4 core structure, the electronic transitions induced by the functional ligands can be clearly elucidated by combined experimental and computational studies. It is reveal that the low-energy transitions of the ferrocene-containing clusters C1 and C2 mainly involve the Fe 3d → Ti6O4 core metal-to-core charge transfer (MCCT) transition. The introduction of ferrocenecarboxylate ligands into the Ti6-oxo clusters significantly reduced the band gap to 2.2 eV (C1) and 1.9 eV (C2) relative to that of 3.6 eV for the benzoate substituted cluster C3. The electron-withdrawing effect of the TFBDC ligand remarkably promotes the PEC activity of C2.

A long-range emissive mega-Stokes inorganic-organic hybrid material with peripheral carboxyl functionality for As(v) recognition and its application in bioimaging.

We demonstrate a strategy for the recognition of As5+ in aqueous solution using a red-emissive probe based on a perylene-Cu2+ ensemble decorated with peripheral free carboxyl functionality. Single crystal analysis helped us to understand the chemical structure of the probe. To the best of our knowledge, this is the first probe for arsenic detection which emits in the red region (λem = 600 nm). The perylene-Cu2+ ensemble exhibited a mega-Stokes shift (>100 nm) with a high degree of selectivity upon interaction with As5+, which indicated that the present probe has the potential to be used as a turn-on optical sensor for selective detection of As5+ with fewer experimental limitations. The detection limit was found to be 26 nM. Inspired by its good emissive properties, the ensemble was further explored for imaging As5+ in live cells. Because of its long-range emissive nature, no autofluorescence from the cellular species was observed during the imaging process. The probe was evaluated to be non-toxic and successfully permeated the cell membrane without the help of any permeabilizing agent to image As5+.

Au nanorods modulated NIR fluorescence and singlet oxygen generation of water soluble dendritic zinc phthalocyanine

A novel cyano-terminated zinc phthalocyanine (ZnPc-CN) exhibiting visible near infrared (vis-NIR) emitting around 690nm in N,N-dimethylformamide (DMF) solvent has been synthesized. Furthermore, the peripheral cyano groups of newly synthesized zinc phthalocyanine were hydrolyzed in strong basic solution, leading to water soluble carboxylated zinc phthalocyanine (ZnPc-COOH) with completely quenched fluorescence in aqueous solution. Interestingly, we found that the NIR fluorescence of aqueous ZnPc-COOH was dramatically recovered in the presence of gold nanorods (Au NR), which was due to the alternation of ZnPc-COOH molecules self-assembling via electrostatic interaction between cetyltrimethylammonium bromide (CTAB) on the surface of Au NR and peripheral carboxyl of ZnPc-COOH. In addition, ZnPc-COOH/Au NR conjugates demonstrated an improved singlet oxygen generation, which could be served as potential bioimaging probe and photosensitizer for photodynamic therapy.

Synthetic Methodology for the Fabrication of Porous Porphyrin Materials with Metal-Organic-Polymer Aerogels.

A promising fabrication strategy used for designing porous porphyrin materials and a group of rigid carboxyl porphyrins based metal-organic-polymer aerogels (MOPAs) has been proposed recently. These newly synthesized MOPAs were exemplarily characterized by FT-IR, UV-vis-DRS, EDS, PXRD, TGA, SEM, TEM, and gas sorption measurements. A gelation study has shown that solvents, molar ratio, temperature, and peripheral carboxyl number in porphyrins all affect gel generation. The MOPA series exhibit eminent thermal stability, high removal efficiency in dye adsorption, versatile morphologies, and permanent tunable porosity; also the BET surface areas fall within the range 249-779 m(2) g(-1). All of the mentioned properties are significantly superior to some other porous materials, which enable these compounds to be potential candidates for dye uptake, gas storage, and separation.

Effect of Lateral Size of Graphene Quantum Dots on Their Properties and Application.

Well-defined graphene quantum dots (GQDs) are crucial for their biological applications and the construction of nanoscaled optoelectronic and electronic devices. However, as-synthesized GQDs reported in many works assume a very wide lateral size distribution; thus, their apparent properties cannot truthfully reflect intrinsic properties of the well-defined GQDs, and more importantly, the applications of GQDs will be affected and limited as well. In this work, we demonstrated that different sized GQDs with a narrow size distribution could be obtained via gel electrophoresis of the crude GQDs prepared through a photo-Fenton reaction of graphene oxide (GO). It is illustrated that the photoluminesce (PL) emissions of the well-defined GQDs originated mainly from the peripheral carboxylic groups and conjugated carbon backbone planes through fluorescence and UV-vis spectroscopies. More importantly, our findings challenge the notion that the excitation wavelength dependent PL property of the as-synthesized GQDs is the intrinsic property of the size-defined GQDs. Preliminary data at the cellular level indicated that the small sized GQDs exhibit weaker quenching DNA dye ability but higher toxicity to the cells compared to that of the as-synthesized GQDs. This discovery is essential to explore applications of the GQDs in pharmaceutics and to understand the origin of the optoelectronic properties of GQDs.

Tailoring the Structure of Two‐Dimensional Self‐Assembled Nanoarchitectures Based on NiII–Salen Building Blocks

The synthesis of a series of Ni(II) -salen-based complexes with the general formula of [Ni(H2 L)] (H4 L=R(2) -N,N'-bis[R(1) -5-(4'-benzoic acid)salicylidene]; H4 L1: R(2) =2,3-diamino-2,3-dimethylbutane and R(1) =H; H4 L2: R(2) =1,2-diaminoethane and R(1) =tert-butyl and H4 L3: R(2) =1,2-diaminobenzene and R(1) =tert-butyl) is presented. Their electronic structure and self-assembly was studied. The organic ligands of the salen complexes are functionalized with peripheral carboxylic groups for driving molecular self-assembly through hydrogen bonding. In addition, other substituents, that is, tert-butyl and diamine bridges (2,3-diamino-2,3-dimethylbutane, 1,2-diaminobenzene or 1,2-diaminoethane), were used to tune the two-dimensional (2D) packing of these building blocks. Density functional theory (DFT) calculations reveal that the spatial distribution of the LUMOs is affected by these substituents, in contrast with the HOMOs, which remain unchanged. Scanning tunneling microscopy (STM) shows that the three complexes self-assemble into three different 2D nanoarchitectures at the solid-liquid interface on graphite. Two structures are porous and one is close-packed. These structures are stabilized by hydrogen bonds in one dimension, while the 2D interaction is governed by van der Waals forces and is tuned by the nature of the substituents, as confirmed by theoretical calculations. As expected, the total dipolar moment is minimized.

Alkylene-bridged viologen dendrimers: versatile cell delivery tools with biosensing properties.

The synthesis of two types of viologen dendrimers with peripheral carboxyl groups is described. Their interaction with plasmid DNA and CT-DNA and the influence of time evolution and electrolyte on dendriplex formation have been electrochemically investigated. A negative potential shift appearing in the cyclic voltammograms of the dendrimers indicates dendriplex formation on the time scale of 15 to 19 minutes, i.e. similar to those determined empirically for other dendrimer types. The presence or absence of the negative potential shift can be used to check the stability towards sodium chloride and different cell growth media directing to sucrose for cell incubation experiments. The electrolyte content of commercially available cell growth media inhibits the dendriplex formation in solution prior to plasmid addition. Furthermore, a low salt stability of 20 mM sodium chloride for viologen dendriplexes has been confirmed, also recommending the use of lysosomotropic sucrose. The two types of viologen dendrimers have been combined with two plasmids differing in the number of base pairs. Four immortal cell lines have been tested to check the suitability of viologen dendriplexes as gene delivery systems. Probably due to the absence of terminal amino groups and endosomolytic substances only a small transfection efficiency of dendriplexes was achieved at low pH, generally excluding in vivo applications. With the larger pHSV-eGFP plasmid (5743 bp) no transfected cells were observed indicating a preference for shorter plasmids.

Assembly of Graphene Oxide at Water/Oil Interfaces: Tessellated Nanotiles

The interfacial assembly of graphene oxide (GO) at the water/oil interface and its kinetics were systematically studied. GO nanosheets were found to segregate to the water/oil interface and interact with quaternized block copolymer chains by the peripheral carboxyl groups on the GO. If the interfacial area is decreased, then GO, assembled at and confined to the interface, jams and then buckles. An analysis of the kinetics of the assembly processes leads to the conclusion that the diffusion of GO to the interface is the rate-determining step. The morphology of the jammed GO film was investigated, and TEM images show that GO sheets form a mosaic or tile across the whole oil/water interface.

A naphthalocyanine based near-infrared photosensitizer: Synthesis and in vitro photodynamic activities

A hydrophilic near-infrared (NIR) photosensitizer featuring a naphthalocyanine core and peripheral carboxylate acid groups was synthesized and characterized. Its photophysical and photochemical properties were studied and compared with phthalocyanine. Due to the extended π-conjugation, both the Q band and fluorescence emit of this naphthalocyanine bathochromically shift to NIR region. It also exhibits superior NIR photodynamic efficiency to phthalocyanine as evidenced by high efficiency in generating singlet oxygen (ΦΔ=0.66) and in vitro phototoxicity toward Hela human cervical cancer cells. Therefore, this novel naphthalocyanine could potentially be a NIR photosensitizer for photodynamic therapy.