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Synthesis, photophysical behaviour and metal ion signalling ability of 3-component systems, I and II, comprising a 4-aminophthalimido moiety as fluorophore, a dimethylene spacer and two different azacrown receptors, are reported. The fluorescence quantum yields and lifetimes of both the systems have been found to be significantly lower than that of the parent fluorophore indicating the occurrence of photoinduced electron transfer (PET) between the terminal moieties. PET is found to be more efficient in II, presumably due to the presence of more than one electron-donating centre in the receptor moiety. Fluorescence decay behaviour of the systems suggests a through-space nature of PET. The systems exhibit off-on fluorescence signalling in the aprotic media in the presence of several metal ions, some of which are well known for their fluorescence quenching abilities. Diazacrown derivative, II, appears to be a somewhat better signalling system than the monoazacrown derivative, I.

The IR absorption and Raman spectra of the following complex compounds based on thiocyanates and crown ethers have been studied: KSCN-18-crown-6, KSCN-dibenzo-18-crown-6, NaSCN-dibenzo-18-crown-6, and NaSCN-benzo-15-crown-5. The shape of the contour of the spectral line corresponding to the stretching vibration ν1(CN) of the thiocyanate ion in the indicated compounds in the temperature interval involving solid and liquid phases have been investigated for the first time. The reorientation parameters and molecular-relaxation characteristics of the thiocyanate ion in the crown compounds have been calculated. It is found that an increase in temperature leads to gradual freeing of cations and to the properties of crown compounds becoming identical to those of pure salt melts.

This paper reports the synthesis of two angiotensin II analogues with tyrosine-functionalized 5,5-bicyclic thiazabicycloalkane dipeptide mimetics replacing the Tyr(4)-Ile(5) residues. The preparation of these analogues relies on the synthesis and incorporation of an alpha,alpha-disubstituted chimeric amino acid derivative and on-resin bicyclization to a cysteine residue. The synthesized analogues both displayed high angiotensin AT(2)/AT(1) receptor binding preferences and had AT(2) receptor affinities in the same low nanomolar range as angiotensin II itself. Conformational analysis, using experimental constraints derived from NMR studies, indicated that the Tyr(4) and His(6) residues in one of the angiotensin II analogues were in close proximity to each other.

We report the synthesis and the functional studies of multiple crown alpha-helical peptides designed to form artificial ion channels. The approach combines the versatility of solid phase peptide synthesis, the conformational predictability of peptidic molecules, and the solution synthesis of crown ethers with engineerable ion-binding abilities. Several biophysical methods were employed to characterize the activity and the mode of action of these crown peptide nanostructures. The 21 residue peptides bearing six 21-EC-7 turned out to facilitate the translocation of ions in a similar fashion to natural ion channels.

4-tert-Butylcalix[4]arene and 18-crown-6 react with NaH in THF to form the complex [(18-crown-6)(THF)Na4(4-tert-butylcalix[4]arene-4H)]2·3THF (1). Analogously, the reaction with 4-tert-butyltetrathiacalix[4]arene in DMF results in the formation of [(18-crown-6)Na(dmf)1.5]2[(4-tert-butyltetrathiacalix[4]arene-4H)2Na6(dmf)2] (2) The X-ray analysis of 1 shows an Na6O6 skeleton consisting of two fused open heterocubanes. Two Na+ ions are encapsulated in the cavities of the calix[4]arene units. Additionally, two peripheral Na+ ions, each surrounded by a crown ether and one THF ligand, are connected to the central Na6O6 skeleton by one bridging oxygen of the calix[4]arene. In contrast, 2 contains the highly symmetrical anion [(4-tert-butyltetrathiacalix[4]arene-4H)2Na6(dmf)2]2− and crown-ether-stabilized cations. While 1 shows a dynamic process in solution above 40 °C, the structure of the highly symmetrical compound 2 remains stable at higher temperatures. The solid-state structure of the potassium complex [(dibenzo-18-crown-6)K4(4-tert-butylcalix[4]arene-4H)(THF)3]2·4THF (4) is similar to 1; however, the calix[4]arene units in the open heterocubane structure of 4 are shifted less than half a diameter to one another than in the sodium complex 1. According to the 1H NMR spectra complex 3a, containing 18-crown-6, has a very similar structure to the related complex 4. Both 1 and 4 absorb carbon dioxide in THF and are active CO2-transfer reagents towards 2-fluoropropiophenone; complex 2 is much less active. This clearly demonstrates the subtle influence of the structure of the alkali metal complexes on the CO2 reactivity in these types of compounds. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)

The syntheses of 1,3-bis(α-picolyloxy)-p-tert-butylcalix[4]arene crown-6 and 1,1'-binaphthalene-2,2'-diyl crown-6 title conformers have been achieved by two complementary synthetic strategies, which differ in the order in which the polyether loop and the pendant picolyl groups are introduced. The structure and conformation of all new compounds have been firmly established by NMR spectroscopy, and further proven by X-ray analysis for the intermediate p-tert-butyl-25,27-(1,1'-binaphthalene-2,2'-diyl-crown-6)-26,28-dihydroxycalix[4]arene. Within each set of conformers, the nature of the polyether chain has little or no influence on the overall conformation of the calixarene platform. The alkali metal ion binding selectivities of the two series of calixarenes have been evaluated in competitive complexation experiments by electrospray ionization mass spectrometry. In the p-tert-butylcalix[4]arene crown-6 series, partial cone and 1,3-alternate conformers show a peak selectivity for the larger Cs+ ions, while the cone one preferentially binds the smaller Na+ ions. On the other hand, the cone and 1,3-alternate binaphthyl-containing analogues show a preference for Na+ ions, the partial cone being quite unselective.

Two novel regioisomeric calix[4]arene derivatives (2 and 3), decorated with two aza[18]crown-6 units at vicinal (1,2) or diagonal (1,3) positions of the upper rim, were synthesized. The catalytic activities of their dinuclear Ba2+ complexes were investigated in the ethanolysis of esters 8-11, endowed with a carboxylate anchoring group. Major results are as follows: 1) the two metal ions in the dinuclear catalysts work together in a cooperative fashion; 2) the vicinal calix[4]arene catalyst 2 is far superior to its diagonal regioisomer 3 in the reactions of all of the investigated esters; and 3) the distance between the carboxylate and ester carbonyl, which increases regularly from 8 to 11, influences reactivity of catalytic ester cleavage in a way that is decidedly suggestive of the importance of a good match between ester size and metal-to-metal distance. However, the superiority of the vicinal catalyst 2 relative to 3 cannot be explained on the basis of the putative match of ester size to intermetal distance, thus providing an indication that additional, still poorly understood effects may contribute significantly to catalytic efficiency.

Two-armed lariat ethers having double bonds present in their side arms form stable complexes with sodium and potassium cations. When the double bonds are positioned appropriately, cation-π interactions are observed between the neutral double bonds and the macroring- bound cation as demonstrated by X-ray crystallography.

Cyclic trimeric perfluoro-o-phenylenemercury (o-C6F4Hg)3 (1) is able to bind hexacyanoferrate(III) and nitroprusside anions to form complexes {[(o-C6F4Hg)3]2[Fe(CN)6]}3− and {[(o-C6F4Hg)3]2[Fe(CN)5NO]}2−, respectively, which contain one anionic species per two macrocycles. According to X-ray diffraction data, the complexes have unusual sandwich structures wherein the anionic guest is located between the planes of two molecules of 1 and is coordinated to each of these through two types of Fe–C–N–Hg bridges. One type is the simultaneous coordination of a cyanide ligand to all three Hg centres of the cycle. The other type is the coordination of a cyanide group to a single Hg atom of the macrocycle. In both types, the bonding of the anionic guest with the macrocyclic host is accomplished with the participation of π-electrons of the cyanide ligands. The synthesized compounds are the first examples of host–guest complexes of a macrocyclic multidentate Lewis acid with anionic metal complexes.

The interaction between the title compound, bis(coronand) 8,and the diarylmagnesium compounds Ph2Mg and (p-tBuC6H4)2Mg in diethyl ether leads to the formation of 1:2 complexes (9 and 10, respectively), irrespective of the initial ratio of the components. In [D8]toluene, the three complex types can be discerned by 1H NMR spectroscopy: double side-on (9a, 10a), side-on/rotaxane (9b, 10b), and, to a very minor extent, double rotaxane (9c, 10c). In the case of 10a and 10b, the temperature dependence showed that rotaxane formation is enthalpically favored at the expense of a more negative entropy. As crystals suitable for structure determination could not be obtained from 9 and 10, the interaction of 8 with the sterically less demanding Hg(SCN)2 was studied. In this case, analogous pseudorotaxanes are formed exclusively, and both the 1:2 complex [8·{Hg(SCN)2}2] (11) and its 1:1 analogue 12 were observed. The double rotaxane structure of 11 was confirmed by X-ray crystal structure determination. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)

Metal ions are superb at templating the synthesis of small macrocycles that are decorated with Lewis basic sites. However, for the synthesis of larger macrocycles, or the synthesis of macrocycles devoid of an array of Lewis basic sites, metal ions are less useful. Here we demonstrate that resorcinarenes can be used as templates to engender the efficient formation of large crown ethers. A three step process of 1). tethering moieties to the template, 2). linking those moieties, and 3). then cleaving off the template leads to the efficient formation of a family of aromatic crown ethers. If adaptable, this approach will prove useful for the construction of macrocycles that are hard to obtain from a step-wise synthesis.

A new series of crown compounds crownopaddlanes 3a–c bearing three cyclobutane rings were prepared by means of intramolecular [2+2] photocycloaddition of styrene derivatives. The yield of crownopaddlane 3b possessing five ethereal oxygen atoms was remarkably high 52% with the addition of sodium borofluoride in the photoreaction system. As this template effect suggests, 3b showed extraordinarily high Na+-selectivity with high efficiency on the liquid–liquid extraction of alkali metal picrates, though 3a having four ethereal oxygen atoms did not extracted any cations in this system. The high Na+-selectivity of 3b was further clarified by the equilibrium stability constants (log Ka) for Na+ (5.85) and K+ (2.91) in acetonitrile solution. The complexation of 3b to Na+ cation was also examined by X-ray crystallography. Crownopaddlane 3c bearing six ethereal oxygen atoms also efficiently and selectively extracted alkali metal cations, compared with conventional 18-crown-6 derivatives.

An X-ray diffraction (XRD) analysis of the title crystals has been carried out: space group P2_1/c, a=12.834(2), b=13.342(3), c=11.462(2) A, β=111.15(1)°, Z=4; 3983 unique reflections collected; R=0.040. The molecular structure of this new crown compound has been determined.

A series of promising benzoazacrown ethers with the nitrogen atom conjugated with the benzene ring were synthesized using a novel synthetic procedure based on stepwise transformation of the macroheterocycle. The structures and spectral properties of the resulting benzoazacrown ethers and their complexes with Ca2+ were studied by X-ray diffraction and 1H, 13C, and 15N NMR spectroscopy including the 2D NOESY technique. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)

The binding of a diiminoplatinum(II) complex of 4-ethynylbenzo-15-crown-5 to divalent metal ions such as Mg2+ or Zn2+ is accompanied by substantial enhancement of emission intensity (1035- and 870-fold increase, respectively, with 40 equivalents of metal salt) at λmax ≈ 555 nm; H+, Cd2+ and alkali-metal ions cause minor enhancement of the photoluminescence (⩽ 10-fold) under similar conditions. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)

Crowned chromenes − four novel naphthopyrans (chromenes) bearing monoaza-12-crown-4, -15-crown-5, -18-crown-6, and a noncyclic analogue at the 5-position − were synthesized, and their photochromism in acetonitrile was examined in the presence of alkali and alkaline-earth metal ions. Incorporation of crown ether units to chromene moieties facilitated to a great extent both the thermal isomerization and photoisomerization of the chromene moiety, reflecting the metal-ion-binding ability of the crown ether moiety. Comparison of the crowned chromenes with the corresponding crowned spirobenzopyrans reveals that photochromism of the crowned chromene reflects an interaction between the metal ion and the crown ether moiety that is stronger than that of the crowned spirobenzopyran, and shows only positive photochromism with significant red-shifts in the UV/Vis absorption spectra, in contrast to the crowned spirobenzopyrans reported previously. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)

Control over the conformational flexibility of p-sulfonatocalix[6]-arene in the solid state is possible in the presence of varied stoichiometric amounts of [18]crown-6 and selected lanthanide(III) chlorides. Complexes 1 and 2 have the calixarene in the elusive "up-up" double cone conformation, whilst complex 3 has the calixarene in the centrosymmetric "up-down" double partial cone conformation, whereby it acts as a divergent receptor. Complex 1 has a double "molecular capsule" arrangement which is composed of two p-sulfonatocalix[6]arenes shrouding two [18]crown-6 molecules, also with both coordinated and homoleptic aquated lanthanide ions around the hydrophilic sulfonate rims of the calixarenes. Complex 2 has a "ferris wheel" arrangement with one lanthanide metal centre coordinated to a sulfonate group and another coordinated to the crown ether whilst tethered to a sulfonate group of the calixarene. Complex 3 forms from a solution with large excess of [18]crown-6, and possesses a crown ether molecule in each of the partial cones and has homoleptic aquated lanthanide ions involved in a complicated hydrogen-bonding regime within the extended structure.

DFT calculations are reported for a series of tin- and crown-ether-based host compounds {i.e., the trimethyl derivatives [18]-crown-6-C6H3COOSn(CH3)3 and [15]-crown-5-C6H3COOSn(CH3)3} capable of binding cations and anions simultaneously. The B3LYP functional together with the 6-31G* basis set was used for the atoms C, H, N, O, S, Na and K and the 3-21G* basis set for Sn in order to obtain insights into the factors determining the nature of the interactions of these compounds with the neutral molecules acetone and H2O, the SCN− anion, and the Na+ and K+ cations. The interaction strength pattern with these molecules was explained by the use of a series of reactivity descriptors such as the Fukui function, hardness, local softness, and the MEP (molecular electrostatic potential). In all cases studied in this paper, the complexes with Na+ were more stable than those with K+, correlating with the size of the cation and the volume available in the crown ether. Moreover, this finding is also in accordance with the greater hardness of Na+ relative to K+, in combination with the hard environment of the crown ether moiety. This region was also analysed by computation of electrostatic potentials, which showed that highly negative values are associated with the inside region of the cavity of the crown, this region thus being amenable to electrophilic attack. The HSAB principle, characterising the reactive sites on the basis of local softness and the Fukui function, provided a firm explanation of the reactivity of the tin atom of the crown ether benzocarboxylate towards SCN−, acetone and water. The HSAB concept was also successfully used to explain the preference of the tin atoms in both crown ethers to bind with the nitrogen atom rather than the sulfur atom of SCN−. This result is a confirmation that the tin atoms in the compounds under consideration behave as hard atoms. Overall, these results fit remarkably well with previous experimentally measured NMR spectroscopy data and demonstrate that the interactions of this kind of molecules can be predicted and interpreted by the use of DFT calculations and DFT-based reactivity descriptors, as well as MEP calculations. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)

The spectroscopic properties of two uranyl crown ether complexes, [UO2(18-crown-6)]2+ and [UO2(dicyclohexano-18-crown-6)]2+, dissolved in acetonitrile and propylene carbonate were studied. UV/VIS and magnetic circular dichroism (MCD) spectra were recorded, as well as emission and excitation spectra. The inclusion complexes formed, have a distorted D3d symmetry, which is common for a crown ether ring, coordinated with a central metal ion. The electronic transitions and vibrational progressions are identified in a D∞h, D3d and D3 distortion scheme. Relaxation of the selection rules by vibronic coupling with the fundamental vibrations of uranyl is discussed.

The design and applications of photochromic crown compounds are reviewed here. Such compounds exhibit the possibility of distinct photochemical control of metal-ion complexation, based on the ionic interactions of their photoionized photochromic moieties. Crowned spirobenzopyran derivatives which the authors designed, when isomerized to their corresponding merocyanine form by UV irradiation, can afford an additional binding site for a metal ion complexed by their crown ether moiety in a sophisticated way, i.e., by the six-membered chelate formation with the phenolate oxygen atom and the crown-ether-ring nitrogen atom. The crowned spirobenzopyrans, therefore, have their metal-ion complexing properties modified remarkably by photoirradiation, like the crowned spironaphthoxazines that are more photolabile than the spirobenzopyran derivatives. Crowned spirobenzothiopyrans possess an affinity to softer metal ions such as silver ion, which promotes their photoisomerization to the open form. Crowned bis(spiroben...

The reaction of cyclic trimeric perfluoro-o-phenylenemercury (o-C6F4Hg)3 (1) with the polyhedral [B12H11SCN]2– anion in THF at 20 °C affords the {[(o-C6F4Hg)3](B12H11SCN)}2– (4) and {[(o-C6F4Hg)3]2(B12H11SCN)}2– (5) complexes. Complex 5 was isolated as the tetrabutylammonium salt. X-ray diffraction analysis showed that this complex has a bent-sandwich structure in which the [B12H11SCN]2– anion is located between the planes of two molecules 1 and is coordinated to both these molecules through B—H—Hg bridges and S—Hg bonds. The stability constants of complexes 4 and 5 in THF (20 °C), which were determined from the IR spectroscopic data, are 16 L mol–1 and 992 L2 mol–2, respectively.

A method for the synthesis of previously unknown nitro derivatives of benzoazacrown compounds in which nitrogen is conjugated with the benzene ring, based on readily available benzocrown ethers used as synthons, has been developed. This approach can serve as a useful tool in the synthesis of diverse benzoazacrown derivatives.

Condensation reactions between 4'-formyl-5'-hydroxybenzo-15-crown-5and 2-aminopyridine, 2-amino-6-methylpyridine, 2-amino-4-methylpyridine or2-(aminomethyl)furan yielded the new laterally functionalized crown ethers1–4. The crown compounds 1–3 form crystalline 1:1 (Na+:ligand) complexes 1a–3a with sodium perchlorate. Ligands and complexes have been characterized by elemental analyses, IR, UV-Vis, 1H-, 13C-NMR and mass spectra. The tautomeric equilibria (phenol-imine, O...H–N and keto-amine, O...H–N forms) have been systematically studied by using UV-Vis absorption spectra. The spectra of the ligands 1–4 and complexes 1a–3a were recorded in polar, non-polar, acidic, and basic media. In solutions of polar solvents, tautomeric interconversion of the Schiff base into the keto-amine form has been observed. A crystal structure [monoclinic, space group P21/c,a = 14.292(2), b = 9.449(6), c = 16.059(2) A, β = 114.20(1)°,V = 1978.4(13) A3, Z = 4 and Dx = 1.314 g cm-3] shows that compound 4 is in the form of phenol-imine in solid state. There is a strong intramolecular [O–H...N 1.78(6), O...N 2.581(7), O–H 0.89(6) A and N...H–O 148.4(5)°] hydrogen bond between the phenolic oxygen and imine nitrogen atoms. The C=N imine bond reveals a trans planar (1E) configuration. The molecules stack in columns parallel to the a/c plane of the unit cell.

A catalytic amount of lipophilic 18-crown-6 ether BBC in a biphasic H2O/toluene KCl solution is successfully applied for several conjugate addition reactions.

Two compounds of EuII with benzo-18-crown-6, triaqua(benzo-18-crown-6)europium(II) diperchlorate (1) and triaqua(benzo-18-crown-6)europium(II) perchlorate hydrate benzo-18-crown-6 solvate (2), were synthesized by electrochemical reduction. The coordination environment of the metal cation in both cases contains six O atoms of the crown ligand and three water molecules. The first complex display strong blue luminescence with a maximum at 425 nm. The excitation spectra do not show any significant energy transfer from the benzo rings to europium. (© Wiley-VCH Verlag GmbH, 69451 Weinheim, Germany, 2002)

Lipoyl imidazolide reacts with aza-15-crown-5 (1,4,7,10-tetraoxa-13-azacyclopentadecane) or aza-18-crown-6 (1,4,7,10,13-pentaoxa-16-azacyclooctadecane) to afford new N-lipoylated azacrown compounds in good yields. These compounds can be transformed into 1,3-dithiols and amines by reduction with complex hydrides of the disulfide and/or amide group of the lipoyl chain. The new pendant-arm macrocycles react as heteroditopic ligands by forming dithiolate and disulfide complexes with the ‘soft’ metal ions Ni2+ and Pd2+, respectively, and an amine complex with the ‘hard’ Li+ ion. Semiempirical and DFT calculations on the complexation of a lithium ion give a most favourable structure in which the azacrown and two solvent molecules are in contact with the metal but not the pendant arm.

The present paper reports the crystal structure and luminescent properties of bis(benzo-15-crown-5)europium(II) diperchlorate. The structure is composed of complex bis(benzo-15-crown-5)europium(II) cations and perchlorate anions. The complex cation is centrosymmetric, and the metal ion is surrounded by 10 oxygen atoms of two ligand molecules. The compound shows very bright luminescence at 23450 cm−1. The emission parameters (wavelength and the average lifetime of the excited state) are compared to those previously reported for the analogous complex in methanol solutions. (© Wiley-VCH Verlag GmbH, 69451 Weinheim, Germany, 2002)

N-Thiophosphorylated thioureas, of general formula [(i-PrO) 2 P(S)NHC(S)] 2 Z (Z = f , y -diamino(oxy)alkyl or 1,10-diaza-18-crown-6), in the form of potassium salts, react with a number of soft ions (Cd 2+ , Zn 2+ , Co 2+ , Ni 2+ , Pd 2+ ) to form novel dimeric complexes. The cadmium (Z = HN(CH 2 ) 2 NH), palladium (Z = HN(CH 2 ) 2 O(CH 2 ) 2 NH), and cobalt (Z = 1,10-diaza-18-crown-6) complexes were analyzed by x-ray crystallography. In the former complex, crown cavities remain free. This fact will allow us to obtain "guest-host" complexes with alkali metal cations.

Metalloporphyrins bearing two crown ether moieties (benzo-15-crown-5) at the 5- and 15-postions have been prepared by condensation of 4′-formyl-benzo-15-crown-5 with either unsubstituted or meso-aryl-substituted dipyrromethanes, followed by oxidation and metallation. The meso-meso-coupled ZnII diporphyrin Zn4 was prepared by the oxidative coupling of Zn1 with AgPF6. UV/vis, fluorescence, and 1H NMR spectroscopic studies revealed that addition of K+ and Rb+ to solutions of monomeric porphyrin derivatives M1 (M = 2 H, Zn, Co, Ni, Pd, Cu) in CHCl3:MeCN (2:1 v/v) induced face-to-face dimerization with high stability constants (ca. 1015−1019M−3). 1H NMR analysis showed that the two Zn1 molecules in the face-to-face dimer were packed more closely than in TPP-type ZnII porphyrin bearing four crown ethers (Krishnan et al, J. Am. Chem. Soc.1982,104, 3643), but such dimerization was hardly detected for 10,20-diphenylated ZnII porphyrin Zn2, probably due to steric hindrance exerted by the meso phenyl groups. meso-Monoarylated ZnII porphyrin Zn3 exhibited a comparably large stability constant for formation of the face-to-face dimer with the meso-aryl substituents pointing outward. Coordination of 4-dimethylaminopyridine to CoII porphyrin was shown to be stronger than the interaction of K+ with the crown ether, thereby dissociating the face-to-face dimer (Co1)2 into six-coordinated monomeric CoII porphyrin 5. The diporphyrin Zn4 formed extended linear aggregates upon addition of K+ and Rb+, owing to the divergent disposition of the crown ether substituents. (© Wiley-VCH Verlag GmbH, 69451 Weinheim, Germany, 2002)

Chemistry of sucrose emphasizing regio- and stereoselective transformations performed at the terminal positions (C-1′ and/or C-6 and/or C-6′) is reviewed. 2,2′,3,3′,4-Penta-O-benzyl sucrose is proposed as particularly useful substrate for the preparation of modified derivatives such as amines, uronic acids, crown ether analogues with incorporated sucrose backbone, and so-called “higher sucroses”, i.e. compounds elongated at either “end” by up to 9 carbon atoms. Application of benzyl protecting groups makes possible synthesis of free sucrose analogues by simple removing of the protecting groups by hydrogenolysis without affecting the very labile glycosidic bond.

The influence of metal ion interaction with crowned spirobenzopyrans on the photoisomerization behavior was investigated through the use of various solvents, crowned spirobenzopyrans, and metal ions. Studies on the photoisomerization behavior of crowned spirobenzopyrans in various solvents revealed that solvation of the phenolate anion moiety in the merocyanine form induced photoisomerization back to the spiropyran form, giving rise to negative photochromism. Metal ion interaction with the phenolate anion moiety similarly caused photoisomerization back to the spiropyran form, while that with the crown ether moiety just produced a polar environment and its influence on photoisomerization behavior was dependent on the affinity of the metal ion captured by the crown ether moiety for the phenolate anion. Therefore, photochromic switching of crowned spirobenzopyrans between positive and negative to control the metal ion interaction with the phenolate anion moiety through the crown ether moiety is possible. This finding suggests a molecular design method for crowned spirobenzopyrans showing desired ion-responsive photochromism.

Stereochemistry of [2+2]- and [1+1]-macrocylization of cis-4-cyclohexene-1,2-dicarboxylic acid with 1,2-dibromoethane, 1,3-dichloro-2-propanol, and 1,5-dichloro-3-oxapentane was studied. The reaction of cis-4-cyclohexene-1,2-dicarboxylic acid with 1,2-dibromoethane according to the [2+2]-cyclization scheme gave a mixture of stereoisomeric macroheterocycles with cis,syn,cis- and cis,anti,cis-junction of the polyether and cyclohexene rings. In the reaction of cis-4-cyclohexene-1,2-dicarboxylic acid with 1,5-dichloro-3-oxapentane, a mixture of crown compounds with cis,anti,cis- and cis-junction of the polyether and cyclohexene rings was obtained. The structure of the products was established on the basis of their chemical transformations and spectral data.

The synthesis of two new 9-phenylacridino-18-crown-6 ether type sensor molecules [1 and (R,R)-2] was accomplished. The cation recognition ability of the achiral sensor molecule 1 towards various ions was studied in acetonitrile by UV/Vis and fluorescence spectroscopies. Our studies revealed the binding of Ag+, Cd2+, Ni2+, Pb2+, Zn2+ and NH4+ ions by the latter molecule. Selectivity of the chiral dimethyl-substituted analogue (R,R)-2 was studied toward the enantiomers of the hydrogen perchlorate salts of 1-phenylethylamine, 1-(1-naphthyl)ethylamine, phenylglycine methyl ester and phenylalanine methyl ester using fluorescence spectroscopy.

Interactions of different hydrophilic (His, Asp, Glu,) and hydrophobic (Ala, Phe, Tyr, Trp) amino acids in water with a scorpiand aza-macrocycle (L1) containing a pyridine group in the ring and its derivative (L2) bearing a naphthalene group in the tail have been analysed by potentiometric and calorimetric measurements. Theoretical calculations corroborate that major attractive forces that hold the adduct together are hydrogen bonds and salt-bridges, even though other interactions such as π-stacking or NH(+)⋯π may contribute in the case of hydrophobic amino acids and L2. Calorimetric measurements indicate that the interactions between L1 and the different amino acids are principally driven by entropy, often associated with solvation/desolvation processes.

International audience; N,N'-Bis(triazoly)diaza[18]crown-6 and Corresponding diaza[15]crown-5 ethers were synthesized by means of click chemistry. The interaction of these ligands with Ni-II, Cu-II, and Zn-II cations were studied by UV/Vis and H-1 and C-13 NNIR spectroscopy. The solid-state structure of Ni-II and Zu(II) complexes formed by the diaza[18]crown-6 ligand were determined by means of X-ray crystallography. The Ni-II complex is centrosyrnmetric; the geometry around the metal ion is slightly distorted octahedral whereby the equatorial sites were occupied by four N atoms, and the axial positions by two O atoms that come from the crown moiety. For the Zn'' diaza[18]crown-6 complex, an irregular octahedral coordination was observed whereby the metal ion is asymmetrically placed in the macrocyclic cavity. The equatorial plane is occupied by two N and two O atoms of the crown moiety, and to N atoms of the triazolyl motifs on the pendant arms occupy the axial positions. The diamagnetic character of the Zn'' ion allows its structural study in solution by NNIR spectroscopy. A dynamic beh avior was observed at room Lem- perEaure, which coriesporids to the displacement. ion between the bond end and the nonbond end of the macrocycle. This movement results in an S4-symmetrical structure in solution. Quantum chemical calculations at the DFT level have allowed us to interpret the experimental results observed in the solid state for the symmetry of the complexes in terms of covalent and noncovalent interactions, which favor the centrosymmetric and irre. gular octahedral coordination modes, respectively. Only the structure of the Cu-II complex with N,N'-bis(triazolyl)diazal[5]crown-5 ligand has been investigated in the solid state, for which a pentagonal bipyramidal coordination sphere was observed. This coordination geometry was confirmed in solution in MeCN by UV/Vis spectroscopy, and also for the Zn-II complex by NMR spectroscopy. In the case of the Ni-II complex, a structural modification was suggested in solution in MeCN based on the UV/Vis spectrum. The rearrangement of heptadentate coordination to hexadentate is proposed

A library of dendronized cyclotriveratrylene (CTV) crowns substituted with chiral, racemic, or achiral peripheral alkyl chains, including enantiopure R and S branched alkyls, "racemic by mixture", "racemic by synthesis", n-octyl, and n-dodecyl groups was synthesized. In solvophobic solvents and in bulk they self-assemble in helical columns. Their solution and bulk shape-persistent supramolecular structures were determined by a complementary combination of circular dichroism (CD) and UV in solution and thin film, microspot CD in thin film, differential scanning calorimetry combined with fiber X-ray diffraction, computer simulation, and molecular models. In solution, self-assembly via a cooperative mechanism generates single-handed columns from enantiopure CTVs and mixtures of right- and left-handed columns from racemic by mixture, racemic by synthesis, other combinations of R and S, and even from achiral compounds. In bulk state all supramolecular columns form a 3D hexagonal crystalline phase, Φ(h)(k) (P6₃ symmetry), that can be obtained only from single-handed columns and a columnar hexagonal 2D liquid crystal, Φ(h). The highest order Φ(h)(k) consists of enantiopure single-handed columns that are slightly distorted 12-fold triple helices. The "hat-shaped" dendronized CTV assembles in bent-branch pine-tree columns that allow interdigitation of alkyl groups in adjacent columns regardless of their direction. Enantiomerically rich, racemic, and achiral compositions undergo deracemization in the crystal state by transfer of the transient disc-like conformer of dendronized CTV from column to column during crown inversion. Solid state NMR experiments identified motional processes that allow such transfer. This unprecedented supramolecular chiral self-sorting will impact the creation of functions in complex systems.

The 3d-4f mixed metallacrowns frequently show single-molecule magnetic behavior. We have used magnetic Compton scattering to characterize the spin structure and orbital interactions in three isostructural metallacrowns: Gd2Mn4, Dy2Mn4, and Y2Mn4. These data allow the direct determination of the spin only contribution to the overall magnetic moment. We find that the lanthanide 4f spin in Gd2Mn4 and Dy2Mn4 is aligned parallel to the Mn 3d spin. For Y2Mn4 (manganese-only spin) we find evidence for spin delocalization into the O 2p orbitals. Comparing the magnetic Compton scattering data with SQUID studies that measure the total magnetic moment suggests that Gd2Mn4 and Y2Mn4 have only a small orbital contribution to the moment. In contrast, the total magnetic moment for Dy2Mn4 MCs is much larger than the spin-only moment, demonstrating a significant orbital contribution to the overall magnetic moment. Overall, these data provide direct insight into the correlation of molecular design with molecular magnetic properties.

This review focuses on synthesis, structure and binding properties of crown compounds and their open-chain analogues containing a trithiadiazapentalene building block. This heterocyclic unit favours in particular the complexation and solvent extraction of the soft transition metal ions Ag(I), Pd(II), Hg(II) and Au(III). The redox active system trithiadiazapentalene/trithiotriuret introduced into a crown ring allows the control of Ag(I) and Hg(II) phase transfer in solvent extraction experiments. Crystal structures of metal complexes with these pentaleno crown compounds show significant differences of both SS bond lengths of the trithiadiazapentalene unit and package arrangements in the cell.

Remarkably, four hydrogen atoms have been regioselectively removed from the 1,1',3,3'-positions of ferrocene in a single reaction leading to the formation of the new macrocyclic host-guest complex [{Fe(C5 H3 )2 }Na4 Mg4 {iPr2 N}8 ]. This novel addition to the s-block metal inverse crown family possesses a tetrasodium-tetramagnesium amido (Na4 Mg4 N8 )4+ ring to complete a series of 8, 12, 16, and 24-membered rings.

It has been shown by IR and NMR spectroscopy that cyclic trimeric perfluoro-o-phenylenemercury (o-C6F4-Hg)3 (1) is capable of binding closo-[B10H10]2- and closo-[B12H12]2- anions to form complexes [[(o-C6F4Hg)3](B10-H10)]2- (2), [[(o-C6F4Hg)3]2(B10H10)]2-(3), [[(o-C6F4Hg)3](B12H12)]2- (4), and [[(o-C6F4Hg)3]2(B12H12)]2- (5). According to IR data, the bonding of the [B10H10]2- and [B12H12]2- ions to the macrocycle in these complexes is accomplished through the formation of B-H-Hg bridges. Complexes 2, 3, and 5 have been isolated in analytically pure form and have been characterized by spectroscopic means. X-ray diffraction studies of 3 and 5 have revealed that these compounds have unusual sandwich structures, in which the polyhedral di-anion is located between the planes of two molecules of 1 and is bonded to each of them through two types of B-H-Hg bridges. One type is the simultaneous coordination of a B-H group to all three Hg atoms of the macrocycle. The other type is the coordination of a B-H group to a single Hg atom of the cycle. According to X-ray diffraction data, complex 2 has an analogous but half-sandwich structure. The obtained complexes 2-5 are quite stable; their stability constants in THF/acetone (1:1) at 20 degrees C have been determined as 1.0 x 10(2)Lmol(-1), 2.6 x 10(3)L(2)mol(2), 0.7 x 10(2)Lmol(-1), and 0.98 x 10(3)L(2)mol(-2), respectively.