Recent progress on supramolecular luminescent assemblies based on aurophilic interactions in solution

The development of supramolecular systems showing aurophilic interactions in solution is gaining much attention in the last years. This is due to the intriguing photophysical properties of gold(I) complexes, which usually confer to these supramolecular assemblies interesting luminescent properties, as well as the possibility of morphological modulation, through fine tuning of inter-and intramolecular aurophilic interactions, in synergy with the formation of other supramolecular contacts. In this work, an overview of the advances made in this area since 2015 is presented. A large variety of systems showing different spectroscopical and structural topologies has been reported. Moreover, these supramolecular assemblies have proven to be useful in a wide range of application

Circular dichroism of anthocyanidin 3-glucoside self-aggregates

“NOTICE: this is the author’s version of a work that was accepted for publication in Phytochemistry. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. A definitive version was subsequently published in Phytochemistry Volume 88, April 2013, Pages 92–98. DOI 10.1016/j.phytochem.2012.12.011 ."“NOTICE: this is the author’s version of a work that was accepted for publication in Phytochemistry. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. A definitive version was subsequently published in Phytochemistry Volume 88, April 2013, Pages 92–98. DOI 10.1016/j.phytochem.2012.12.011 .""Self-association constants for the flavylium cations of the six most common anthocyanidin 3-glucosides were determined by circular dichroism (CD) and UV–Vis spectroscopy. Along with previous 1H NMR results, all measurements were consistent with a monomer–dimer model. The CD spectra of the antho-cyanidin 3-glucosides were similar to the analogues 3,5-diglucosides. All dimers of the anthocyanidin 3-glucosides exhibited left-handed CD signals, with petunidin-3-glucoside and myrtillin having the most intense signals. In addition, the magnitude of the molar ellipticity, [h], was generally higher for the 3-glucosides than for the 3,5-diglucosides. For all six anthocyanins studied, the CD absorption spectra of their dimers showed evidence of the splitting of the monomer absorption into lower (J) and higher (H) energy bands. The angle and the distance between the dipolar moments of the two monomers comprising the dimer were obtained from the lower energy absorption band. While the angle was more or less similar in all six dimers, the separation distance between the monomer dipole moments differed dramatically. The intensity of the CD signal displayed a linear dependence with the inverse square of the dipole moment distances.

Tripodal gold(I) polypyridyl complexes and their Cu+ and Zn2+ heterometallic derivatives. Effects on luminescence

Three gold(I) tripodal complexes containing the tris(2-pyridylmethyl)amine (TPA) ligand coordinated to Au-PR3 moieties (PR3 = 1,3,5-triaza-7-phosphatricyclo[3.3.1.13.7]decane, PTA (1), 3,7-diacetyl-1,3,7-triaza-5-phosphabicyclo[3.3.1]nonane, DAPTA (2) and triphenylphosphane (3)) were prepared together with a cage-like structure containing triphosphane 1,1,1-tris(diphenylphosphinomethyl)ethane (4). The luminescence of these complexes has been studied and they show a red shift upon the formation of heterometallic complexes by reaction with Zn(NO3)2, CuCl and [Cu(CH3CN)4]BF4. The different coordination motifs of the Zn2+ and Cu+ heterometallic species and the resulting changes in the recorded absorption, emission and NMR spectra were analysed and supported by TD-DFT calculations

Study of the effect of the chromophore and nuclearity on the aggregation and potential biological activity of gold(I) alkynyl complexes

The synthesis and characterization of four organometallic gold(I) complexes containing different water soluble phosphanes (TPPTS, PTA and DAPTA) and chromophoric units (4-pyridylethynyl and propargyloxycoumarin) is here reported. The analysis of their absorption and emission spectra led us to attribute their luminescent behavior to the chromophoric organic ligands. Moreover, the presence of the gold(I) metal atom has been observed to be the responsible of an efficient intersystem crossing process responsible for the observed phosphorescence emission. Broad emission bands are observed in most cases due to the formation of organized aggregates in solution in agreement with microscopic characterization. Biological activity of the complexes showed very low effects against tumor cell growth but an inhibitory potency against thioredoxin reductase (TrxR). The missing/low cytotoxic effects could be related to a low bioavailability as determined by atomic absorption spectroscopy. Graphical abstract The synthesis, characterization, aggregation and emissive properties of four organometallic gold(I) complexes containing different water soluble phosphanes and chromophoric units is here reported. Biological activity of the complexes showed very low effects against tumor cell growth but an inhibitory potency against thioredoxin reductase (TrxR

Tuning supramolecular aurophilic structures: the effect of counterion, positive charge and solvent

The synthesis of the cationic gold(I) complexes [Au(CuCC5H4N)(CH3-PTA)] X (X = I, 1; X = OTf, 4), [Au(C equivalent to CC5H4N-CH3)(PTA)] X (X = I, 2; X = OTf = 5; PTA = 1,3,5-triaza-7-phosphatricyclo[3.3.1.13.7]decane) and [Au(CuCC5H4N-CH3)(DAPTA)] X (X = I, 3; X = OTf = 6, DAPTA = 3,7-diacetyl-1,3,7-triaza-5-phosphabicyclo[ 3.3.1]nonane) results in cationic complexes with unexpected supramolecular assemblies in water ranging from rod-like structures (1) to vesicles (2 and 3) and square-like structures (5 and 6). These morphologies are completely different from the fibers previously obtained with their parent neutral complexes [Au(C equivalent to C5H4N)(PTA)] and [Au(C equivalent to C5H4N)(DAPTA)]. Nevertheless, the introduction of triflate as a counterion in 1 (complex 4) gives rise to the formation of a highly soluble complex in water which does not display any significant aggregation in solution. These results reveal the importance of the introduction of a positive charge on global supramolecular assemblies and how the counterion can also modify the resulting package. Interestingly, we have also proved that the aggregation of complexes 2, 3, 5 and 6 is also affected by the solvent with direct influence on their absorption and emission properties and the global morphology of the aggregates.Postprint (author's final draft

Polarized supramolecular aggregates based on luminescent perhalogenated gold derivatives

Reaction of [Au(C6F5)(tht)] (tht = tetrahydrothiophene) with 1,3,5-triaza-7-phosphaadamantane (PTA) and 3,7-diacetyl-1,3,7-triaza-5-phosphabicyclo[3.3.1]-nonane (DAPTA) leads to the formation of [Au(C6F5)(phosph)] (phosph = PTA, 1; phosph = DAPTA, 2). The compounds are slightly soluble in water and aggregate at higher concentrations giving rise to the formation of needle- and rod-like structures (1) and well-organized spherical aggregates (2). Compounds 1 and 2 were reacted with AgPF6 giving rise to the formation in all cases of luminescent water soluble 1:1 Au·Ag heterometallic complexes, as evidenced by X-ray crystal structure determination. The use of different silver salts that differ on the counterion induces changes on the resulting luminescence and aggregation morphology

Supramolecular tripodal Au(I) assemblies in water. Interactions with pyrene fluorescent probe

The synthesis of three gold(I) tripodal complexes derived from tripropargylamine and containing the water soluble phosphines PTA (1, 3,5-triaza-7-phosphaadamantane), DAPTA (3,7-diacetyl-1,3,7-triaza--phosphabicyclo[3.3.1]nonane) and TPPTS (triphenylphosfine-3,3',3''-trisulfonic acid trisodium salt) is here described. The three complexes are observed to give rise to the formation of supramolecular aggregates in water and very long fibers. This property has been analyzed by means of 1H-NMR spectroscopy at different concentrations and SAXS. The results point out the important role of the phosphine moieties as the main enthalpic or entropic contribution in the resulting Gibbs energy of aggregates formation. The tripodal structure of the three complexes together with the presence of gold(I) atoms make them ideal candidates to interact with hydrophobic molecules also in water. For this, the interaction with pyrene in this solvent has been evaluated with successful results in all three complexes. The highest association constant corresponds to 2 as the host. DFT studies indicates the location of pyrene in the tripodal cavity as the most stable conformation. The interaction with pyrene has been additionally studied within cholate hydrogel matrixes pointing out the stability of the resulting host:guest adducts in the different medium

Thermodynamic and Kinetic Properties of a New Myrtillin–Vescalagin Hybrid Pigment

[EN] During red wine maturation in contact with oak wood, C-glucosidic ellagitannins can react with anthocyanins, leading to new pigments. In this work the thermodynamic and kinetic constants of the network pH-dependent equilibrium of a new myrtillin (delphinidin 3-O-glucoside)−vescalagin hybrid pigment (1-deoxyvescalagin-(1β→8)-myrtillin) have been determined by UV−visible absorption and stopped-flow experiments and compared to those determined for myrtillin. The vescalagin substitution at the C-8′ center of myrtillin entails important variations in the pigment behavior upon pH changes. The hybrid pigment showed lower pK′a and pKa values and a much higher value of Kt. As a consequence, at moderately acidic pH values (4 < pH < 6), the percentage of the hemiketal is much lower and the quinoidal base and the (E)-chalcone represent higher percentages relative to those for myrtillin. Therefore, the hybrid pigment can provide in slightly acidic or neutral solutions an exceptionally different color compared to that of myrtillin

LYTAG-driven purification strategies as a key to integrate and intensify the downstream processing of monoclonal antibodies

Monoclonal antibodies (mAbs) are currently the most important class of recombinant protein therapeutics in the biotechnological and biopharmaceutical industry with more than 250 mAbs currently undergoing clinical trials. High titer producing cultures and complex mixtures containing high cell densities, together with an increasing growing demand for highly pure mAbs is making recovery and purification processes hot targets for improvement and opens important technological challenges in mAbs manufacturing platforms. This work explores the use of an affinity dual ligand based on a choline binding polypeptide tag (LYTAG) fused with the synthetic antibody Z domain (LYTAG-Z) as a tool to integrate and optimized the downstream processing of mAbs. Upon addition of this ligand to an animal cell culture broth, antibody-LYTAG-Z complexes are formed which can be easily captured and separated from host cell impurities by affinity partitioning in aqueous two-phase systems (ATPS) composed of polyethylene glycol –PEG, as PEG molecules have the ability to binding to the choline binding sites of LYTAG. Integration of clarification and primary mAbs recovery was successfully accomplished using a system composed of 6% PEG 3350 Da and 7% dextran 500,000 Da in which an extraction yield of 89% and a clarification higher than 95% were achieved. IgG-rich phases were further processed by chromatography, using three different strong anion exchange matrices charged with quaternary methyl amines (a choline analogue) – CIMmultus QA, HiTrap Q FF and gPore NW Q. A two-elution method was developed for the separation of the antibody-LYTAG-Z complexe, allowing simultaneous purification of the antibody and recovery of the ligand. The process was successfully scale-up 10000 times allowing a global antibody recovery of 70% with a purity of 89% and enabling 100% cell removal

Tuning supramolecular aurophilic structures: the effect of counterion, positive charge and solvent

The synthesis of the cationic gold(I) complexes [Au(C≡CC5H4N)(CH3-PTA)]X (X = I, 1; X = OTf, 4), [Au(C≡CC5H4N-CH3)(PTA)]X (X = I, 2; X = OTf = 5; PTA = 1,3,5-triaza-7-phosphatricyclo[3.3.1.13.7]decane) and [Au(C≡CC5H4N-CH3)(DAPTA)]X (X = I, 3; X = OTf = 6, DAPTA = 3,7-diacetyl-1,3,7-triaza-5- phosphabicyclo[3.3.1]nonane) gives cationic complexes showing unexpected supramolecular assemblies in water going from rod-like structures (1) to vesicles (2 and 3) and square-like structures (5 and 6). These morphologies are completely different from the fibers previously obtained with their parent neutral complexes [Au(C≡C5H4N)(PTA)] and [Au(C≡C5H4N)(DAPTA)]. Nevertheless, the introduction of triflate as counterion in 1 (complex 4) gives rise to the formation of highly soluble complex in water which does not display any significant aggregation in solution. These results reveal the importance of the introduction of a positive charge on the global supramolecular assemblies and how the counterion can modify also the resulting package. Interestingly, we have also proved that the aggregation of complexes 2, 3, 5 and 6 is also affected by the solvent with direct influence on their absorption and emission properties and the global morphology of the aggregates