Application of electronic circular dichroism in the study of supramolecular systems

Defying strain in the synthesis of an electroactive bilayer helicene

Visible-light-induced oxidative cyclization of a phenanthrene framework overcomes immense strain to yield a bilayer perylene-diimide helicene.

We report the synthesis of a bilayer chiral nanographene incorporating a [7]helicene scaffold and two perylene-diimide (PDI) subunits. Twofold visible-light-induced oxidative cyclization of a phenanthrene framework selects for the desired PDI-helicene, despite the immense strain that distinguishes this helicene from two other accessible isomers. This strain arises from the extensive intramolecular overlap of the PDI subunits, which precludes racemization, even at elevated temperatures. Relative to a smaller homologue, this PDI-helicene exhibits amplified electronic circular dichroism. It also readily and reversibly accepts four electrons electrochemically. Modifications to the core phenanthrene subunit change the fluorescence and electrochemistry of the PDI-helicene without significantly impacting its electronic circular dichroism or UV-visible absorbance.

A computational study of the vibrationally-resolved electronic circular dichroism spectra of single-chain transoid and cisoid oligothiophenes in chiral conformations

We simulate the vibronic profile of the electronic circular dichroism (ECD) spectra of oligothiophenes in cisoid and transoid chiral arrangements. We consider oligomers of different lengths, from two to fifteen units, and investigate extensively how the ECD spectral shapes depend on the inter-ring torsions. In general, the molecular structures we consider are not stationary points of the ground state potential energy surface. Therefore, in order to perform vibronic calculations, we present a new computational protocol able to define reduced-dimensionality models where the effect of the off-equilibrium modes is removed. This is done adopting a description of the vibrational motions in curvilinear internal coordinates, and vertical harmonic models coupled with an iterative application of projectors to define energy Hessians, and therefore effective normal modes, in the space complementary to the one of the off-equilibrium coordinates. Although we consider both Franck-Condon and Herzberg-Teller contributions, the results show that transoid twisted ribbons always give rise to monosignated ECD spectra, while bi-signated and multi-signated spectra are expected for cisoid helices. These findings are explained on the basis of the different transition strengths of the lowest electronic states imparted by the different spatial arrangement, that is almost linear for transoid structures and more globular for cisoid ones. We predicted the chiroptical response of a large number of possible molecular arrangements. These data are employed to critically discuss the experimental ECD of polythiophenes in different experimental conditions, forming either aggregates or host-guest complexes. The method here proposed to perform vibronic calculations in reduced-dimensionality models is of general applicability and its potential interest goes beyond the practical application presented here.

Supramolecular Hemoprotein Assembly with a Periodic Structure Showing Heme-Heme Exciton Coupling

A supramolecular assembly of units of cytochrome b₅₆₂ with externally attached heme having intermolecular linkages formed via the heme-heme pocket interaction was investigated in an effort to construct a well-defined structure. The engineered site for surface attachment of heme at Cys80 in an N80C mutant of cytochrome b₅₆₂ provides the primary basis for the formation of the periodic assembly structure, which is characterized herein by circular dichroism (CD) spectroscopy and high-speed atomic force microscopy (AFM). This assembly represents the first example of the observation of a split-type Cotton effect by heme-heme exciton coupling in an artificial hemoprotein assembly system. Molecular dynamics simulations validated by simulated CD spectra, AFM images, and mutation experiments reveal that the assembly has a periodic helical structure with 3 nm pitches, suggesting the formation of the assembled structure is driven not only by the heme-heme pocket interaction but also by additional secondary hydrogen bonding and/or electrostatic interactions at the protein interfaces of the assembly.

Diameter-Dependent Optical Absorption and Excitation Energy Transfer from Encapsulated Dye Molecules toward Single-Walled Carbon Nanotubes

The hollow cores and well-defined diameters of single-walled carbon nanotubes (SWCNTs) allow for creation of one-dimensional hybrid structures by encapsulation of various molecules. Absorption and near-infrared photoluminescence-excitation (PLE) spectroscopy reveal that the absorption spectrum of encapsulated 1,3-bis[4-(dimethylamino)phenyl]-squaraine dye molecules inside SWCNTs is modulated by the SWCNT diameter, as observed through excitation energy transfer (EET) from the encapsulated molecules to the SWCNTs, implying a strongly diameter-dependent stacking of the molecules inside the SWCNTs. Transient absorption spectroscopy, simultaneously probing the encapsulated dyes and the host SWCNTs, demonstrates this EET, which can be used as a route to diameter-dependent photosensitization, to be fast (sub-picosecond). A wide series of SWCNT samples is systematically characterized by absorption, PLE, and resonant Raman scattering (RRS), also identifying the critical diameter for squaraine filling. In addition, we find that SWCNT filling does not limit the selectivity of subsequent separation protocols (including polyfluorene polymers for isolating only semiconducting SWCNTs and aqueous two-phase separation for enrichment of specific SWCNT chiralities). The design of these functional hybrid systems, with tunable dye absorption, fast and efficient EET, and the ability to remove all metallic SWCNTs by subsequent separation, demonstrates potential for implementation in photoconversion devices.

Light-driven chiroptical photoswitchable DNA assemblies mediated by bioinspired photoresponsive molecules

We show that the incorporation of chiral bioinspired photochromic compounds into inherently chiral DNA matrices enables the building of smart nanoscale photoswitchable chiroptical assemblies tunable over a wide range of wavelengths. Moreover, the use of light as external trigger affords precise control of the resulting hybrid DNA nanostructures, and their chiroptical activities can be spatially modulated without photochemical fatigue.

Giant intrinsic circular dichroism of prolinol-derived squaraine thin films

Molecular chirality and the inherently connected differential absorption of circular polarized light (CD) combined with semiconducting properties offers great potential for chiral opto-electronics. Here we discuss the temperature-controlled assembly of enantiopure prolinol functionalized squaraines with opposite handedness into intrinsically circular dichroic, molecular J-aggregates in spincasted thin films. By Mueller matrix spectroscopy we accurately probe an extraordinary high excitonic circular dichroism, which is not amplified by mesoscopic ordering effects. At maximum, CD values of 1000 mdeg/nm are reached and, after accounting for reflection losses related to the thin film nature, we obtain a film thickness independent dissymmetry factor g = 0.75. The large oscillator strength of the corresponding absorption within the deep-red spectral range translates into a negative real part of the dielectric function in the spectral vicinity of the exciton resonance. Thereby, we provide a new small molecular benchmark material for the development of organic thin film based chiroptics.

Short Azapeptides of Folded Structures in Aqueous Solutions

Building folded short peptides that are driven by the intramolecular hydrogen bonding in aqueous solutions remains challenging because of their highly competitive intermolecular hydrogen-bonding interactions with water solvent molecules that would have favored the extended conformations. Here, we show folded β-turn structures in acyl amino acid-based N-amidothioureas, the nonclassic azapeptides, in aqueous solutions, as well as in solid-state and organic solvents, by X-ray crystal structures, DFT calculations, 1D and 2D NMR spectra, and absorption and CD spectra. The achiral phenylthiourea chromophore acts as a CD reporter for the β-turn structure that communicates the chirality of the amino acid residue to the achiral thiourea moiety and the relative intensity of the intramolecular hydrogen bond that stabilizes the turn structure. The amidothiourea moiety represents a versatile structural framework for folded short peptides in aqueous environments.

Diasteroselective multi-component assemblies from dynamic covalent imine condensation and metal-coordination chemistry: mechanism and narcissistic stereochemistry self-sorting

Self-assembly of a modified tris(2-pyridylmethyl)amine TPMA ligand, zinc(ii) or cobalt(ii) ions, and amino acids have been used effectively as stereo dynamic optical probes for the determination of the enantiomeric excess of free amino acids either using Electronic or Vibrational Circular Dichroism (CD and VCD). Herein, we report the mechanistic and stereochemical study of the self-assembly process which reveals a complex equilibrium in solution where even small variations in the experimental conditions can profoundly affect the final products of the reaction. In particular, variation on the metal stoichiometry switch give rises to an entirely enantio narcissistic self-assembly of the structure.

Molecular simulations of self-assembling bio-inspired supramolecular systems and their connection to experiments

In bionanotechnology, the field of creating functional materials consisting of bio-inspired molecules, the function and shape of a nanostructure only appear through the assembly of many small molecules together. The large number of building blocks required to define a nanostructure combined with the many degrees of freedom in packing small molecules has long precluded molecular simulations, but recent advances in computational hardware as well as software have made classical simulations available to this strongly expanding field. Here, we review the state of the art in simulations of self-assembling bio-inspired supramolecular systems. We will first discuss progress in force fields, simulation protocols and enhanced sampling techniques using recent examples. Secondly, we will focus on efforts to enable the comparison of experimentally accessible observables and computational results. Experimental quantities that can be measured by microscopy, spectroscopy and scattering can be linked to simulation output either directly or indirectly, via quantum mechanical or semi-empirical techniques. Overall, we aim to provide an overview of the various computational approaches to understand not only the molecular architecture of nanostructures, but also the mechanism of their formation.

Device-Compatible Chiroptical Surfaces through Self-Assembly of Enantiopure Allenes

Chiroptical methods have been proven to be superior compared to their achiral counterparts for the structural elucidation of many compounds. To expand the use of chiroptical systems to everyday applications, the development of functional materials exhibiting intense chiroptical responses is essential. Particularly, tailored and robust interfaces compatible with standard device operation conditions are required. Herein, we present the design and synthesis of chiral allenes and their use for the functionalization of gold surfaces. The self-assembly results in a monolayer-thin room-temperature-stable upstanding chiral architecture as ascertained by ellipsometry, X-ray photoelectron spectroscopy, and near-edge X-ray absorption fine structure. Moreover, these nanostructures anchored to device-compatible substrates feature intense chiroptical second harmonic generation. Both straightforward preparation of the device-compatible interfaces along with their chiroptical nature provide major prospects for everyday applications.

Circular dichroism studies of low molecular weight hydrogelators: The use of SRCD and addressing practical issues

Circular dichroism (CD) spectroscopy has been used extensively for the investigation of the conformation and configuration of chiral molecules, but its use for evaluating the mode of self-assembly in soft materials has been limited. Herein, we report a protocol for the study of such materials by electronic CD spectroscopy using commercial/benchtop instruments and synchrotron radiation (SR) using the B23 beamline available at Diamond Light Source. The use of the B23 beamtime for SRCD was advantageous because of the unique enhanced spatial resolution achieved because of its highly collimated and small beamlight cross section (ca. 250 μm) and higher photon flux in the far UV region (175-250 nm) enhancing the signal-to-noise ratio relative to benchtop CD instruments. A set of low molecular weight (LMW) hydrogelators, comprising two Fmoc-protected enantiomeric monosaccharides and one Fmoc dipeptide (Fmoc-FF), were studied. The research focused on the optimization of sample preparation and handling, which then enabled the characterization of sample conformational homogeneity and thermal stability. CD spectroscopy, in combination with other spectroscopic techniques and microscopy, will allow a better insight into the self-assembly of chiral building blocks into higher order structural architectures.

Self-assembly and chiroptical properties in supramolecular complexes of adenosine phosphates and guanidinium-bispyrene

Supramolecular systems that respond to the hydrolysis of adenosine phosphates (APs) are attractive for biosensing and to fabricate bioinspired self-assembled materials. Here, we report on the formation of supramolecular complexes between an achiral guanidinium derivative bearing two pyrene moieties, with each of the three adenosine phosphates: AMP, ADP, and ATP. By combining results from circular dichroism spectroscopy and molecular modeling simulations, we explore the induced chirality, the dynamics of the complexes, and the interactions at play, which altogether provide insights into the supramolecular self-assembly between APs and the guanidinium-bispyrene. Finally, we identify the chiroptical signals of interest in mixtures of the guanidinium derivative with the three APs in different proportions. This study constitutes a basis to evolve toward a chiroptical detection of the hydrolysis of APs based on organic supramolecular probes.

Self-assembly of (boron-dipyrromethane)-diphenylalanine conjugates forming chiral supramolecular materials

Herein, we present the synthesis of a series of boron-dipyrromethane (BDP) derivatives bearing diphenylalanine (FF) at their meso position via amide bond coupling. The BDP-FF bioconjugates are able to form self-assembled materials with different morphologies. By altering various parameters such as the protecting group of the FF peptide or the solvent system of the self-assembly process, we were able to obtain either fibrillar or spherical nanostructures. Furthermore, we confirmed that both the formation as well as the dissociation of the self-assemblies is a reversible procedure that can be achieved by simply altering the solvent mixture. Electronic circular dichroism (ECD) studies demonstrated a characteristic mirror image relationship regarding the F_LF_L and F_DF_D enantiomers, revealing the chiral nature of the obtained materials. Interestingly, an intense excitonic bisignate signal was observed in the ECD spectrum of the fibrillar structures, whereas the spherical assemblies remained ECD silent. What is more, the electronic circular dichroism studies were supported by quantum chemical calculations.

How and How Much Molecular Conformation Affects Electronic Circular Dichroism: The Case of 1,1-Diarylcarbinols

Chiroptical spectra such as electronic circular dichroism (ECD) are said to be much more sensitive to conformation than their non-chiroptical counterparts, however, it is difficult to demonstrate such a common notion in a clear-cut way. We run DFT and TDDFT calculations on two closely related 1,1-diarylmethanols which show mirror-image ECD spectra for the same absolute configuration. We demonstrate that the main reason for the different chiroptical response of the two compounds lies in different conformational ensembles, caused by a single hydrogen-to-methyl substitution. We conclude that two compounds, having the same configuration but different conformation, may exhibit mirror-image ECD signals, stressing the importance and impact of conformational factors on ECD spectra.

Polarization spectroscopy methods in the determination of interactions of small molecules with nucleic acids - tutorial

The structural characterization of non-covalent complexes between nucleic acids and small molecules (ligands) is of a paramount significance to bioorganic research. Highly informative methods about nucleic acid/ligand complexes such as single crystal X-ray diffraction or NMR spectroscopy cannot be performed under biologically compatible conditions and are extensively time consuming. Therefore, in search for faster methods which can be applied to conditions that are at least similar to the naturally occurring ones, a set of polarization spectroscopy methods has shown highly promising results. Electronic circular dichroism (ECD) is the most commonly used method for the characterization of the helical structure of DNA and RNA and their complexes with ligands. Less common but complementary to ECD, is flow-oriented linear dichroism (LD). Other methods such as vibrational CD (VCD) and emission-based methods (FDCD, CPL), can also be used for suitable samples. Despite the popularity of polarization spectroscopy in biophysics, aside several highly focused reviews on the application of these methods to DNA/RNA research, there is no systematic tutorial covering all mentioned methods as a tool for the characterization of adducts between nucleic acids and small ligands. This tutorial aims to help researchers entering the research field to organize experiments accurately and to interpret the obtained data reliably.

Chiral Cu(ii), Co(ii) and Ni(ii) complexes based on 2,2′-bipyridine modified peptoids

Helical peptoids bearing 2,2′-bipyridine, varied in their chiral bulky side chains and their N-terminus form chiral complexes with Cu(ii), Co(ii) and Ni(ii) via intramolecular binding.

EXAT: EXcitonic analysis tool

We introduce EXcitonic Analysis Tool (EXAT), a program able to compute optical spectra of large excitonic systems directly from the output of quantum mechanical calculations performed with the popular Gaussian 16 package. The software is able to combine in an excitonic scheme the single-chromophore properties and exciton couplings to simulate energies, coefficients, and excitonic spectra (UV-vis, CD, and LD). The effect of the environment can also be included using a Polarizable Continuum Model. EXAT also presents a simple graphical user interface, which shows on-screen both site and exciton properties. To show the potential of the method, we report two applications on a a chiral perturbed BODIPY system and DNA G-quadruplexes, respectively. The program is available online at http://molecolab.dcci.unipi.it/tools/. © 2017 Wiley Periodicals, Inc.

Molecular photoswitches mediating the strain-driven disassembly of supramolecular tubules

Chemists have created molecular machines and switches with specific mechanical responses that were typically demonstrated in solution, where mechanically relevant motion is dissipated in the Brownian storm. The next challenge consists of designing specific mechanisms through which the action of individual molecules is transmitted to a supramolecular architecture, with a sense of directionality. Cellular microtubules are capable of meeting such a challenge. While their capacity to generate pushing forces by ratcheting growth is well known, conversely these versatile machines can also pull microscopic objects apart through a burst of their rigid tubular structure. One essential feature of this disassembling mechanism is the accumulation of strain in the tubules, which develops when tubulin dimers change shape, triggered by a hydrolysis event. We envision a strategy toward supramolecular machines generating directional pulling forces by harnessing the mechanically purposeful motion of molecular switches in supramolecular tubules. Here, we report on wholly synthetic, water-soluble, and chiral tubules that incorporate photoswitchable building blocks in their supramolecular architecture. Under illumination, these tubules display a nonlinear operation mode, by which light is transformed into units of strain by the shape changes of individual switches, until a threshold is reached and the tubules unleash the strain energy. The operation of this wholly synthetic and stripped-down system compares to the conformational wave by which cellular microtubules disassemble. Additionally, atomistic simulations provide molecular insight into how strain accumulates to induce destabilization. Our findings pave the way toward supramolecular machines that would photogenerate pulling forces, at the nanoscale and beyond.

Chiral amplification of disodium cromoglycate chromonics induced by a codeine derivative

Chromonic liquid crystals (CLC) are lyotropic phases formed by discotic mesogens in water. Simple chiral dopants such as amino acids have been reported to turn chromonic liquid crystals into their cholesteric counterparts. Here we report a chirality amplification effect in the nematic phase of a 9 wt% disodium cromoglycate (DSCG) lyotropic liquid crystal (LLC) upon doping with a water-soluble codeine derivative. The transition on cooling the isotropic to the nematic phase showed the presence of homochiral spindle-shaped droplets (tactoids). NMR DOSY experiments on a triple gradient probe revealed a small degree of diffusion anisotropy for the alkaloid embedded in the liquid crystal structure. These results in combination with XRD, CD and POM experiments agree with a supramolecular aggregation model based on simple columnar stacks.

Local order and vibrational coupling of the C=O Stretching Mode of γ-Caprolactone in liquid binary mixtures

The isotropic and anisotropic parts Raman spectra of γ-Caprolactone in the binary mixture at different concentrations have been measured. The non-coincidence effect (NCE) of γ-Caprolactone was determined in carbon tetrachloride solution and DMSO solution. The NCE of the ν₁₁(C=O) stretching mode in the γ-Caprolactone/DMSO mixtures exhibits a linear plot, in contrast to that in the γ-Caprolactone/CCl₄ mixtures, which shows an upward (convex) curvature. The reduction and enhancement of the dimer structure (short-range orientational order) of γ-Caprolactone in the γ-Caprolactone/DMSO and γ-Caprolactone/CCl₄ mixtures respectively may play a major role in shifting of peak frequencies, thus the geometries of monomer and dimer of γ-Caprolactone were calculated at the B3LYP-D3/6-311 G (d,p) level of theory. We proposed aggregated model to explain the γ-Caprolactone C=O vibration NCE phenomenon and its concentration effect and found it largely consistent with our experimental findings. Solvent dependent experiment show the value of NCE declined with the increase of the solvent dielectric constant under the same condition which is consistent with the Logan's theory.

Biological effects of α-adrenergic phentolamine on erythrocyte hemeprotein: Molecular insights from biorecognition behavior, protein dynamics and flexibility

Phentolamine is one of the most representative nonselective α-adrenoreceptor blocking agents, which have been proved to be owned various pharmacological actions. Unfortunately, whether erythrocytes in the veins intervene in biological behaviors of such drug are largely obscured. With the aid of multiple biophysical techniques, this scenario was to detailed explore the potential biorecognition between phentolamine and the hemeprotein in the cytosol of erythrocytes, and the influences of dynamic characters of protein during the bioreaction. Steady-state and time-resolved fluorescence data manifested that the biomolecular recognition of phentolamine by hemeprotein was processed through the biopolymer-drug adduct with a moderate strength of 10⁴M^-1. Such procedure causes a reduction in fluorescence intensity of the aromatic tryptophan (Trp) residues, and the R-T transition of the globular protein occurred concurrently. Circular dichroism demonstrated the conclusions of fluorescence essays, viz. biorecognition can induce fairly structural transformation (self-regulation) of protein conformation. Furthermore, one could find that a specific domain for phentolamine is located at the polypeptide chains α₁β₂ interface, and hydrogen bonds, π-conjugated and hydrophobic effects are discovered to be held the lowest energy state of the biomacromolecule-drug biosystem, which overtly matches the outcomes of wet experiments. Meanwhile, several crucial residues such as Trp-37 and Arg-40 were confirmed to have directly noncovalent interactions with phentolamine, and the effect of the heme group on the biomolecule-drug recognition is minimal. Further analyses of molecular dynamics simulation supported that the inherent protein flexibility may notably elicit alterations in some key noncovalent bonds between biomacromolecule and drug during the dynamic biointeraction, which might primarily be attributed to the torsion of drug structure and the conformational changes of essential residues. Undoubtedly, this research will not only help to thoroughly unearth the pharmacological profiles of phentolamine, but to elaborate the impacts of the intrinsic features (i.e. dynamics and flexibility) of critically cellular proteins on the biological conducts of active α-adrenergic blockers.

A high-performance liquid chromatography-electronic circular dichroism online method for assessing the absolute enantiomeric excess and conversion ratio of asymmetric reactions

Asymmetric reactions often need to be evaluated during the synthesis of chiral compounds. However, traditional evaluation methods require the isolation of the individual enantiomer, which is tedious and time-consuming. Thus, it is desirable to develop simple, practical online detection methods. We developed a method based on high-performance liquid chromatography-electronic circular dichroism (HPLC-ECD) that simultaneously analyzes the material conversion ratio and absolute optical purity of each enantiomer. In particular, only a reverse-phase C18 column instead of a chiral column is required in our method because the ECD measurement provides a g-factor that describes the ratio of each enantiomer in the mixtures. We used our method to analyze the asymmetric hydrosilylation of β-enamino esters, and we discussed the advantage, feasibility, and effectiveness of this new methodology.

Chiral discrimination of α-hydroxy acids and N-Ts-α-amino acids induced by tetraaza macrocyclic chiral solvating agents by using 1H NMR spectroscopy

In the field of chiral recognition, reported chiral discrimination by 1H NMR spectroscopy has mainly focused on various chiral analytes with a single chiral center, regarded as standard chiral substrates to evaluate the chiral discriminating abilities of a chiral auxiliary. Among them, chiral α-hydroxy acids, α-amino acids and their derivatives are chiral organic molecules involved in a wide variety of biological processes, and also play an important role in the area of preparation of pharmaceuticals, as they are part of the synthetic process in the production of chiral drug intermediates and protein-based drugs. In this paper, several α-hydroxy acids and N-Ts-α-amino acids were used to evaluate the chiral discriminating abilities of tetraaza macrocyclic chiral solvating agents (TAMCSAs) 1a-1d by 1H NMR spectroscopy. The results indicate that α-hydroxy acids and N-Ts-α-amino acids were successfully discriminated in the presence of TAMCSAs 1a-1d by 1H NMR spectroscopy in most cases. The enantiomers of the α-hydroxy acids and N-Ts-α-amino acids were assigned based on the change of integration of the 1H NMR signals of the corresponding protons. The enantiomeric excesses (ee) of N-Ts-α-amino acids 11 with different optical compositions were calculated based on the integration of the 1H NMR signals of the CH3 protons (Ts group) of the enantiomers of (R)- and (S)-11 in the presence of TAMCSA 1b. At the same time, the possible chiral discriminating behaviors have been discussed by means of the Job plots of (±)-2 with TAMCSAs 1b and proposed theoretical models of the enantiomers of 2 and 6 with TAMCSA 1a, respectively.

C-I···π Halogen Bonding Driven Supramolecular Helix of Bilateral N-Amidothioureas Bearing β-Turns

We report the first example of C-I···π halogen bonding driven supramolecular helix in highly dilute solution of micromolar concentration, using alanine based bilateral I-substituted N-amidothioureas that contain helical fragments, the β-turn structures. The halogen bonding interactions afford head-to-tail linkages that help to propagate the helicity of the helical fragments. In support of this action of the halogen bonding, chiral amplification was observed in the supramolecular helix formed in acetonitrile solution. The present finding provides alternative tools in the design of self-assembling macromolecules.

Porphyrin aggregates decorated MWCNT film for solar light harvesting: influence of J- and H-aggregation on the charge recombination resistance, photocatalysis, and photoinduced charge transfer kinetics

Effect of J- and H-aggregation on the photophysical and photochemical properties.

Ring-locking strategy facilitating determination of absolute optical purity of 2-amino-1-butanol by reverse-phase high-performance liquid chromatography

A concise and efficient reverse-phase high-performance liquid chromatography (RPLC) method has been established for absolute optical purity assay of 2-amino-1-butanol, which is an important synthetic intermediate of various drugs.

Unusual crystal structure and chirality of uridine 5′-monophosphate coordination polymer

The auxiliary ligand effect in the structure and charility of uridine 5′-monophosphate coordination polymer was investigated.