Crown-containing styryl dyes

New crown ether styryl dyes containing various heterocyclic moieties and substituents were synthesized. Thecis andtrans isomers of crown ether styryl dyes and their complexes with metal cations were characterized by their absorption and fluorescence spectra. Based on an analysis of the spectral parameters and the shifts of the absorption and fluorescence maxima upon photoisomerization and complexation, the effects of the nature and structure of the heterocyclic moiety on the photochromism of styryl ionophores were revealed.For Part 12, see Ref. 1.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 129–135, January, 1995.This study was financially supported by the Russian Foundation for Basic Research (Grants No. 94-03-08-531 and 93-03-04-089) and the International Science Foundation (Grant M8QOO).     

Crown-containing butadienyl dyes

Crown-containing butadienyl dyes containing various heterocyclic moieties and azacrown ether fragments were synthesized for the first time. The spatial structures and the absorption and fluorescence spectra of crown-containing butadienyl dyes and their complexes with metal cations were examined. The effects of the nature of the heterocyclic and crown ether fragments on fluorescence and generation of dyes and their complexes with metal cations were revealed based on the spectral data. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 530–541, March, 1999.     

Synthesis and multitopic complex formation of a photochromic bis(crown ether) based on benzobis(thiazole)

2,7-Bis[2-(6,7,9,10,12,13,15,16-octahydro-5,8,11,14,17-pentaoxabenzocyclopentadecen-2-yl)vinyl]-benzo[1,2-d;3,4-d']bisthiazole, 2, with crown ether styryl moieties substituted on a heterocyclic core, was synthesized and its complex forming ability with several metal cations was evaluated in acetonitrile by absorption and fluorescence spectroscopy. The results are compared to those for the analogous ligand possessing a single crown ether styryl moiety. Selective binding of the metal cation at the heterocyclic core of both ligands was observed only for Hg2+. Alkali and alkaline earth cations bind selectively at the crown ether moieties. Stability constants and pure spectra of defined stoichiometry were determined with the use of HYPERQUAD, a least-squares fitting program, and the results were validated in one case by subjecting the titration spectral matrix to singular value decomposition with self-modeling (SVD-SM). The multitopic ligand 2 forms relatively strong 2:2 stoichiometric complexes with K+, among the alkali metal cations, and Ba2+, among the alkaline earth metal cations, and is a promising selective optical sensor for these ions.     

Crown ether styryl dyes

Regio- and stereoselectivity of [2+2]-photocycloaddition in complexes containing crown ether styryl dyes and alkaline-earth metal cations were studied using molecular mechanics. The main assumption is that the rate of the allowed concerted photocycloaddition correlates with the relative energies of the ground states of dimeric adducts, which are treated as pre-reaction complexes, and the resulting cyclobutanes. These energies are estimated by molecular mechanics within the MMX parameterization. The calculated characteristics of different dyes are studied as functions of the structure of the heterocyclic moiety, the structure and size of the N-substituent, the size of the crown ether cycle, and the nature of the metal cation. A comparison between the computational results and the experimental data showed that the observed quantum yield of the reaction is governed by the relative energies of the dimeric complexes and the resulting cyclobutanes as well as by the mutual arrangement of dye molecules in the dimeric complexes. Both factors are closely interrelated. The approach used in this work furnishes an explanation for the experimental data and provides a guideline for supramolecular control of regio- and stereochemistry of cation-dependent [2+2]-photocycloaddition. For Part 24, sec Ref. 1. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 2185–2191, November, 1998.     

Crown ether styryl dyes

New crown ether-containing styryl dyes of the benzothiazole series containing an aza-15-crown-5-ether moiety were synthesized. Thetrans-cis-photoisomerization of these dyes and their analogs was studied; the effect of metal cations on the kinetics of darkcis-trans-isomerization was elucidated. The stability constants of the complexes of thecis-isomers of these dyes with Ca(ClO₄)₂ were estimated. The dramatic increase (by more than three orders of magnitude) in the stability of the complexes on passing from a cationic dye to a betaine was attributed to the formation of an intramolecular bond in thecis-complexes between the sulfo group of theN-substituent and the metal cation located in the cavity of the azacrown-ether moiety.     

Simulation of optical response to complex formation of crown-containing 2-styrylbenzothiazoles with alkaline-earth metals

The photochromic properties and complex formation of 2-styrylbenzothiazoles containing different crown ether moieties with alkaline-earth metals were described using optical methods, NMR spectroscopy, and HPLC. The large ionochromic effect and fluorescence quenching on complex formation with alkali-earth metal cations were found for 2-styrylbenzothiazole containing the phenylazacrown ether moiety. The small ionochromic effect and fluorescence enhancement of complex formation with alkali-earth metal cations were found for 2-styrylbenzothiazole containing the benzocrown ether moiety. cis-Isomers of 2-styrylbenzothiazoles were stable in the dark in acetonitrile. The method for separation of cis-isomers of 2-styrylbenzothiazoles by HPLC was proposed.     

ESR spectroscopy of copper(ii) complexes with aza- and thia-containing crown ethers

Six copper(ii) chloride complexes with crown ethers containing besides oxygen also nitrogen or sulfur atoms in 15- or 18-membered cycle were studied by ESR and electron absorption spectroscopies. Theg and HFI tensor components determined by spectral simulation indicate rhombic symmetry and localization of an unpaired electron on the d _xy orbital for all the complexes. The unpaired electron fractions on - and -type metal ion and ligand AO were estimated from ESR and absorption spectra using LCAO MO method. Both - and -type bond covalences were shown to be greater in these complexes compared to only oxygen-containing crown ether complexes. The temperature dependence of g and A components in some complexes may be due to conformational changes.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 1938–1944, November, 1994.The present work was carried out with financial support from the Russian Foundation for Basic Research (Project 93-03 04089).     

Synthesis of cyanine dyes derived from benzotellurazo‐15‐crown‐5

A series of crown ether cyanine dyes including crown ether styryl cyanine dyes, crown ether merocyanine dyes and crown ether squarylium cyanine dyes (unsymmetric and symmetric) derived from key intermediate 2‐methyl‐5,6(15‐crown‐5)benzotellurazole ( 1 ) were prepared.     

Interaction of Crown Ether‐Annelated Styryl Dyes with Double‐Stranded DNA

DNA‐binding properties of 15‐crown‐5‐derived mono‐ and bis‐styryl dyes were investigated in the presence of calf thymus DNA. To access the factors that influence the DNA association in the series of these ligands, the structure of the molecules was varied by either changing size of the heterocyclic moiety or altering the position of the styryl substituents. The major binding mode for the monostyryl dyes is intercalation. Notably, binding of the dyes to the nucleic acids leads to a fluorescence enhancement by a factor of up to 54. Therefore, these cationic styryl derivatives may be applied as fluorescent “light‐up” probes for DNA detection.     

Effect of arrangement of the styryl fragment on the optical properties and complexation of mono-and bis(styryl)-substituted <Emphasis Type="Italic">N</Emphasis>-methylpyridinium perchlorates containing benzo-15-crown-5 ether moieties

Using ¹H NMR spectroscopy and steady-state and time-resolved electronic spectroscopy, the optical properties of mono-and bis(styryl)pyridinium perchlorates and their complexes with Mg²⁺, Ba²⁺ cations were studied. The stability constants of the complexes were determined using spectrophotometric titration. The formation of inclusion complexes for Mg²⁺ and sandwich type complexes for Ba²⁺ results in fluorescence enhancement and increases the lifetimes of the excited states of the initial bis-styryl ligands. The variation of position of the styryl fragment in the pyridinium aromatic ring gives rise to photochromic crown ethers with different optical and photophysical characteristics and is also an easy route to bis(crown-ethers) of symmetrical and unsymmetrical structure. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 2092–2100, November, 2007.     

Cation binding by a crown-capped porphyrin

The crown ether capped metalloporphyrins (6) form complexes with metal cations; complex formation may be detected by fluorescence quenching for (6, M=ZnII or CuII) and paramagnetic guest cations or, in some cases, by FAB mass spectrometry. Complexation with alkyl ammonium cations was also examined using absorption spectrometry.     

Recoordination of a metal ion in the cavity of a crown compound: a theoretical study. 1. Conformers of arylazacrown ethers and their complexes with Ca2+ cation

Photoinduced recoordination of Ca²⁺ complexes of the photochromic azacrown ethers is studied by the density functional method. The study included model arylazacrown ethers containing various acceptor groups in the aromatic ring in the para position to the azacrown ether moiety and a real azacrown-containing styryl dye. It is found that both free azacrown ethers and their complexes can adopt two types of conformations: (1) axial conformations, in which the aromatic ring axis passing through the crown ether nitrogen N_cr and the opposite atom of the aromatic ring is perpendicular to the root-mean-square (RMS) plane of the crown ether (least-squares fitted plane for all the crown ether atoms), and (2) equatorial conformations, in which the aromatic ring axis only slightly deflects from the RMS plane of the crown ether. In the equatorial conformers, the metal cation is coordinated only to the O atoms of the azacrown ether cycle, the metal—nitrogen bond is broken, and N_cr is conjugated with the aromatic ring. In the axial conformers, the metal cation is additionally coordinated to N_cr. It is found that the presence of an acceptor group bearing a formal positive charge decreases the relative energy of the equatorial conformer and favors metal—nitrogen bond dissociation, which results in the recoordination of the metal cation. However, a long distance between the charged group and N_cr has the reverse effect. The photoinduced recoordination observed in the alkaline-earth metal complexes of the photochromic azacrown ethers is explained by the transitions between the axial and equatorial conformers facilitated by the charge transfer in the excited state of the complex.     

Synthesis,complexation, and <Emphasis Type="Italic">E—Z</Emphasis> photoisomerization of azadithiacrown-containing styryl dyes as new optical sensors for mercury cations

New styryl dyes containing azadithia-15-crown-5 fragments were synthesized. The complexation of these compounds with Ag⁺, Pb²⁺, Cu²⁺, Hg²⁺, and H⁺ cations was studied by ¹H NMR spectroscopy, steady-state, and time-resolved spectroscopy. The stability constants of the complexes were calculated from the spectrophotometric titration data. The photophysical properties and E—Z photoisomerization of styryl dyes and their complexes with mercury and copper(II) cations in acetonitrile were examined. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 495–507, March, 2007. Centre de Physique Moléculaire Optique et Hertzienne-UMR CNRS 5798, Bordeaux University I, 351 Cours de la Libération, 33405 Talence, France.     

Crown-containing styryl dyes

Styryl dyes containing a crown ether group and a heteroaromatic moiety with a sulfoalkylN-substituent (1a,b) undergo photocyclodimerization in acetonitrile in the presence of Mg(ClO₄)₂ to give only the typeA isomer of cyclobutane derivative (2a,b). The photochemical regio- and stereoselectivity of the cycloaddition is explained by self-organization of thetrans-isomers of the styryl dyes upon complexation with the Mg²⁺ cations into dimers with a fixed mutual arrangement of multiple bonds.For part 7, see ref. 1.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1449–1452, August, 1993.     

Properties of cis- and trans-bis(crown ether)s for complexation and extraction of alkali metal picrates

The properties of cis- and trans-bis(crown ether)s containing benzo-15-crown-5 or benzo-18-crown-6 units as complexants and extractants for alkali metal picrates have been studied. The optical spectra suggest that the cis-bis(crown ether)s can form intramolecular 2:1 crown ether unit/cation complexes with particular metal cations easily, while the trans-bis(crown ether)s can form only 1:1 crown ether unit/cation complexes because of the unfavourable trans configuration for the formation of the 2:1 complexes. It was found that the cis isomer possesses much higher extractive power than the trans isomer for the metal cations, which also reflects their complexing properties. The extraction equilibrium constants and thermodynamic quantities have been also evaluated, and the effect of the stereochemical structure of the bis(crown ether) on the complexing and extractive properties is discussed.     

Metal-ion induced FRET in macrocyclic dynamic tweezers

We report here about effective FRET process (73–99%) in mono-Mg²⁺ complexes of symmetrical crown ether bis(styryl) dyes. The FRET process has not been observed in the free state and in binuclear complexes. The formation of mononuclear complex provides two styrylic fragments with appropriate positions of absorption and emission bands for FRET. The other important parameter for FRET is the proper geometric orientation of both chromophores, which attain sandwich conformation with close positioning of complexed and free styryl fragments induced by ion-modulated geometry reorganization of the bis-dye.     

Electro-optical triple-channel sensing of metal cations via multiple signalling patterns

We described two molecular systems containing tricyanovinyl dyes as signalling subunits and crown ether macrocycles as binding sites, which act as triple-channel sensing receptors. Signalling was observed through UV-vis, fluorescence and electro-chemical measurements. With these three techniques sensing of certain metal cations was achieved via multiple signalling patterns.     

Conformation of p-dimethylamino aza styryl dyes

Conformational studies on some p-dimethylamino β-aza and β-aza (with respect to the dimethylamino phenyl ring) styryl dyes derived from quinoline-4, quinoline-2, pyridine-4, pyridine-2, and benzothiazole-2 have been carried out using the quantum mechanical PCILO (perturbative configuration interaction using localized orbitals) method. These molecules may be considered as heterocyclic analogues of benzylidene anilines whose conformations have been studied extensively by both theoretical and experimental methods to explain the difference of their spectra from the isoelectronic benzylidene compounds. The results of the present studies show that the β-aza styryl dyes are nearly planar. In case of β-aza styryl dyes, although the phenyl ring is coplanar with the central atoms, there is a substantial twist of the heterocyclic ring. These results are explained in terms of CT -1 and CT -2 effects and are used as a possible explanation for the observed spectral and sensitization properties.     

“Two‐Point” Self‐Assembly and Photoinduced Electron Transfer in meso‐Donor‐Carrying Bis(styryl crown ether)‐BODIPY–Bis(alkylammonium)fullerene Donor–Acceptor Conjugates

BF₂‐chelated dipyrromethene, BODIPY, was functionalized to carry two styryl crown ether tails and a secondary electron donor at the meso position. By using a “two‐point” self‐assembly strategy, a bis‐alkylammonium‐functionalized fullerene (C₆₀) was allowed to self‐assemble the crown ether voids of BODIPY to obtain multimodular donor–acceptor conjugates. As a consequence of the two‐point binding, the 1:1 stoichiometric complexes formed yielded complexes of higher stability in which fluorescence of BODIPY was found to be quenched; this suggested the occurrence of excited‐state processes. The geometry and electronic structure of the self‐assembled complexes were derived from B3LYP/3‐21G(*) methods in which no steric constraints between the entities was observed. An energy‐level diagram was established by using spectral, electrochemical, and computational results to help understand the mechanistic details of excited‐state processes originating from ¹bis‐styryl‐BODIPY*. Femtosecond transient absorbance studies were indicative of the formation of an exciplex state prior to the charge‐separation process to yield a bis‐styryl‐BODIPY ^{. +}–C₆₀ ^{. −} radical ion pair. The time constants for charge separation were generally lower than charge‐recombination processes. The present studies bring out the importance of multimode binding strategies to obtain stable self‐assembled donor–acceptor conjugates capable of undergoing photoinduced charge separation needed in artificial photosynthetic applications.     

New Poly - and Bis(crown ether)s as Extracting Reagents

Abstract

New poly- and bis(crown ether)s containing benzo-15-crown-5 or benzo-18-crown-6 moieties were synthesized as extracting reagents, and by a preliminary solvent extraction of alkali metal picrates the poly- and bis-(crown ether)s were found to extract the cations capable of forming sandwich-type 2:1 complexes more effectively than their monomeric analogs.