Paracyclophane Ligands Research Articles

Interaction of the Silver(I) Cation with [2.2]Paracyclophane: Experimental and Theoretical Study

AbstractElectrospray ionization mass spectrometry was used to investigate the cation‐π interaction of Ag+ cation with [2.2]paracyclophane. It was found that cationic Ag.([2.2]paracyclophane)+ and Ag.([2.2]paracyclophane)2+ complex species are formed in the gas phase. Further, applying quantum mechanical calculations in the frame of the density functional theory, using B3LYP functional with Def2TZVP basis set, the most probable structures of the proved Ag+ ‐ [2.2]paracyclophane complexes were derived. In the Ag.([2.2]paracyclophane)+ complex, the cation Ag+ is bounded to three carbon atoms of one benzene ring of [2.2]paracyclophane ligand via cation‐π interaction. Quite analogously is bonded also second [2.2]paracyclophane molecule in Ag.([2.2]paracyclophane)2+ complex. The interaction energy, E(int), of Ag.([2.2]paracyclophane)+ complex was calculated to be −220.79 kJ/mol, E(int) of Ag.([2.2]paracyclophane)2+ complex is −362.67 kJ/mol. It is consistent with the formation of the considered Ag+ ‐ [2.2]paracyclophane complex species.

Reaction of the thallium(I) cation with [2.2]paracyclophane: Experimental and theoretical study

Electrospray ionization mass spectrometry was used to investigate the cation-π interaction of Tl+ cation with [2.2]paracyclophane. It was found that 1:1 cationic complex species is formed in the gas phase. Further, applying quantum mechanical calculations in the frame of the density functional theory, applying B3LYP functional with Def2TZVP basis set, the most probable structure of the proved [2.2]paracyclophane – Tl+ complex was derived. In the resulting complex, the cation Tl+ is bounded to six carbon atoms of one benzene ring of [2.2]paracyclophane ligand via cation-π interaction. The interaction energy, E(int), of this cation-π complex was calculated to be −133.59 kJ/mol, which is consistent with the formation of the considered Tl+ – [2.2]paracyclophane complex species.

Solvent extraction of europium(III) trifluoromethanesulfonate into nitrobenzene by using [2.2.2]paracyclophane – Experimental and theoretical study

The extraction constant corresponding to the equilibrium Eu3+(aq) + 3A-(aq) + 1(nb) ⇌ 1 Eu3+(nb) + 3A–(nb) occurring in the two-phase water–nitrobenzene system (A-=CF3SO3-; 1 = [2.2.2]paracyclophane; aq = aqueous phase, nb = nitrobenzene phase) was determined as logKex(Eu3+,3A–) = -5.7 ± 0.1. Further, the stability constant of the 1 Eu3+ complex in nitrobenzene saturated with water was calculated as log Knb(1 Eu3+) = 7.4 ± 0.1. Finally, by using quantum chemical calculations, the most probable conformation of the cationic complex species 1 Eu3+ was derived. In the resulting complex, the “central” cation Eu3+, fully located in the cavity of the parent [2.2.2]paracyclophane ligand, is bound to all three benzene rings of [2.2.2]paracyclophane via cation-π interaction.

Interaction of the lithium cation with [2.2.2]paracyclophane: Experimental and theoretical study

By using electrospray ionization mass spectrometry (ESI-MS), it was proven experimentally that the univalent lithium cation (Li+) forms with [2.2.2]paracyclophane (C24H24) the cationic complex [Li(C24H24)]+. Further, applying quantum chemical DFT calculations, the most probable structure of the [Li(C24H24)]+ complex was derived. In the resulting complex with a symmetry very close to C3, the “central” cation Li+, fully located in the cavity of the parent [2.2.2]paracyclophane ligand, is coordinated to all three benzene rings of [2.2.2]paracyclophane via cation-π interaction. Finally, the interaction energy, E(int), of the considered cation-π complex [Li(C24H24)]+ was found to be –324.7 kJ/mol, confirming the formation of this fascinating complex species as well.

A Pd3L6 supramolecular cage incorporating photoactive [2.2]paracyclophane units

In this work we report two photoactive [2.2]paracyclophane (pCp) ligands and a luminescent Pd3L6 cage incorporating these ligands, which exhibits blue emission both in solution and in the powder state.

2.2]Paracyclophane bis(pyridine)-based metallosupramolecular rhombs in the gas phase: Competitive cleavage of non-covalent and weak covalent bonds.

The gas-phase fragmentation behavior of self-assembled metallo-supramolecular rhombs based on an unusual chiral [2.2]paracyclophane bis(pyridine) ligand is studied by collision-induced dissociation mass spectrometry. The fragmentation patterns strongly depend on the charge state of the respective mass-selected aggregate. For the doubly charged ions, simple symmetric fragmentation is observed in full accordance with previous results reported for related metallo-supramolecular species. The triply charged species cleaves unsymmetrically which can be rationalized by a preferred formation of ions with low charge density. CID of the quadruply charged rhomb reveals a complex fragmentation. Besides ligand oxidation to the radical cation, facile cleavage of the central covalently bound part of the [2.2]paracyclophane ligand takes place which is even preferred over rupture of the weak dative pyridine-Pd bond.

Interaction Between the Rubidium Cation and [2.2.2]Paracyclophane: Experimental and Theoretical Study.

By means of electrospray ionization mass spectrometry (ESI-MS), it was evidenced experimentally that the rubidium cation (Rb+) reacts with the electroneutral [2.2.2]paracyclophane ligand (C24H24) to form the cationic complex [Rb(C24H24)]+. Moreover, applying quantum chemical calculations, the most probable conformation of the proven [Rb(C24H24)]+ complex was solved. In the complex [Rb(C24H24)]+ having a symmetry very close to C3, the "central" cation Rb+, fully located in the cavity of the parent [2.2.2]paracyclophane ligand, is coordinated to all three benzene rings of [2.2.2]paracyclophane via cation-π interaction. Finally, the binding energy, E(int), of the considered cation-π complex [Rb(C24H24)]+ was evaluated as -99.3 kJ/mol, confirming the formation of this fascinating complex species as well. This means that the [2.2.2]paracyclophane ligand can be considered as a receptor for the rubidium cation in the gas phase.

Fascinating interaction of the ammonium cation with [2.2.2]paracyclophane: experimental and theoretical study

ABSTRACTBy means of electrospray ionisation mass spectrometry, it was evidenced experimentally that the ammonium cation (NH4+) reacts with the electroneutral [2.2.2]paracyclophane ligand (C24H24) to form the cationic complex [NH4(C24H24)]+. Moreover, applying quantum chemical calculations, the most probable conformation of the proven [NH4(C24H24)]+ complex was solved. In the complex [NH4(C24H24)]+ having a symmetry very close to C3, the ‘central’ cation NH4+ is coordinated by three strong bifurcated intramolecular hydrogen bonds to the corresponding six carbon atoms from the three benzene rings of [2.2.2]paracyclophane via cation–π interaction. Finally, the interaction energy, E(int), of the considered complex [NH4(C24H24)]+ was evaluated as −625.8 kJ/mol, confirming the formation of this fascinating complex species as well. It means that the [2.2.2]paracyclophane ligand can be considered as an effective receptor for the ammonium cation in the gas phase.

Experimental and Theoretical Study on Cation–π Interaction of the Potassium Cation with [2.2.2]Paracyclophane

By using electrospray ionization mass spectrometry, it was proven experimentally that the univalent potassium cation (K+) forms with [2.2.2]paracyclophane (C24H24) the cationic cluster [K(C24H24)]+. Further, applying quantum chemical DFT calculations, the most probable structure of the [K(C24H24)]+ complex was derived. In the resulting complex with a symmetry very close to C 3, the “central” cation K+, fully located in the cavity of the parent [2.2.2]paracyclophane ligand, is coordinated to all three benzene rings of [2.2.2]paracyclophane via cation–π interaction. Finally, the interaction energy, E(int), of the considered cation–π complex [K(C24H24)]+ was found to be − 614.8 kJ mol−1, confirming the formation of this fascinating complex species as well. It means that the [2.2.2]paracyclophane ligand can be considered as an effective receptor for the potassium cation in the gas phase.

Cation-π interaction of the univalent sodium cation with [2.2.2]paracyclophane: Experimental and theoretical study

By employing electrospray ionization mass spectrometry (ESI-MS), it was proven experimentally that the univalent sodium cation (Na+) forms with [2.2.2]paracyclophane (C24H24) the cationic complex [Na(C24H24)]+. Further, applying quantum chemical DFT calculations, the most probable structure of the [Na(C24H24)]+ complex was derived. In the resulting complex with a symmetry very close to C3, the “central” cation Na+, fully located in the cavity of the parent [2.2.2]paracyclophane ligand, is bound to all three benzene rings of [2.2.2]paracyclophane via cation-π interaction. Finally, the interaction energy, E(int), of the considered cation-π complex [Na(C24H24)]+ was found to be −267.3 kJ/mol, confirming the formation of this fascinating complex species as well.

2.2.2]Paracyclophane as a receptor for the cesium cation in the gas phase

ABSTRACTBy using electrospray ionisation mass spectrometry, it was proven experimentally that the cesium cation (Cs+) forms with [2.2.2]paracyclophane (C24H24) the cationic complex [Cs(C24H24)]+. Further, applying quantum chemical calculations, the most probable structure of the [Cs(C24H24)]+ complex was derived. In the resulting complex with a symmetry very close to C3, the ‘central’ cation Cs+, fully located in the cavity of the parent [2.2.2]paracyclophane ligand, is bound to all three benzene rings of [2.2.2]paracyclophane via cation–π interaction. Finally, the interaction energy, E(int), of the considered cation–π complex [Cs(C24H24)]+ was found to be −73.2 kJ/mol, confirming the formation of this fascinating complex species as well. This means that [2.2.2]paracyclophane can be considered as a receptor for the Cs+ cation in the gas phase.

Double-Strand DNA Breaks Induced by Paracyclophane Gold(I) Complexes.

Gold(I) complexes of ClickPhos [2.2]paracyclophane ligands were synthesized in excellent yields and fully characterized by spectroscopic methods as well as X-ray crystallography. The complexes exhibit a rigid ligand backbone and a triazolyl moiety and were systematically studied with respect to their cytotoxic properties. In combination with the ionic complex [(GemPhos)Au(tht)][ClO4 ] (tht=tetrahydrothiophene), in which the gold(I) atom exhibits a distorted trigonal coordination sphere of two phosphines and a labile tht ligand, their efficiency in cytotoxicity was investigated in HeLa, MCF7, and HCT116 cells as well as in a zebrafish model. Their cytotoxicity and their mechanisms of action are different and involve apoptosis, necrosis, and DNA damage. The compounds presented herein are potent metal-based cytostatics displaying LD50 values from 3.5-38 μm in different tumor cell lines and induce double-strand DNA breaks (DSB) as shown by H2AX phosphorylation (γH2AX) at foci of DSBs.

Experimental and theoretical study on cation–π interaction of the univalent thallium cation with [2.2.2]paracyclophane

By using electrospray ionization mass spectrometry (ESI-MS), it was proven experimentally that the univalent thallium cation (Tl+) forms with [2.2.2]paracyclophane (C24H24) the cationic complex species [Tl(C24H24)]+. Further, employing quantum mechanical DFT calculations, the most probable structure of the [Tl(C24H24)]+ complex was derived. In the resulting complex with a symmetry very close to C3, the ‘central’ cation Tl+ is bound by six bonding interactions to six carbon atoms from the three benzene rings of the parent [2.2.2]paracyclophane ligand via cation–π interaction.

Roadmap towards N‐Heterocyclic [2.2]Paracyclophanes and Their Application in Asymmetric Catalysis

AbstractA novel family of [2.2]paracyclophane derivatives is described. Different substituted pyrazole, triazole and pyrimidine moieties were introduced to the [2.2]paracyclophane scaffold and the products were characterized spectroscopically and by X‐ray structure analysis. These compounds are promising ligands for application in asymmetric catalysis. We show here that one of these ligands can catalyze asymmetric conjugate addition. Furthermore a palladium complex was synthesized by using a hydroxy‐pyrazolyl[2.2]paracyclophane ligand.

NMR-Spectroscopic and Solid-State Investigations of Cometal-Free Asymmetric Conjugate Addition: A Dinuclear Paracyclophaneimine Zinc Methyl Complex

We present herein the first indications for dimeric structures in cometal-free asymmetric conjugate addition reactions of dialkylzinc reagents with aldehydes. These are revealed by nonlinear effect (NLE) studies. A monomer-dimer equilibrium can be assumed which explains the increase of the ee value in the product over time. Also, DOSY NMR spectroscopic measurements indicate the existence of the catalyst as [LZnEt](n) complexes in solution. Additionally, the first X-ray structure of a zinc complex with a [2.2]paracyclophane ligand was determined. The structures of the zinc complexes are supported by DFT calculations of monomeric and dimeric species.

Coordination chemistry of mercury-containing anticrowns. Synthesis and structure of an unusual discrete, double-decker sandwich complex of cyclic trimeric perfluoro- o-phenylenemercury with an aromatic hydrocarbon

The reaction of the three-mercury anticrown ( o-C 6F 4Hg) 3 ( 1) with [2.2]paracyclophane (PCP) yields a complex {[( o-C 6F 4Hg) 3] 2(PCP)} ( 2), having a double-decker sandwich structure in the crystal. The PCP ligand in 2 is located between the mutually parallel planes of the two anticrown units and it coordinates to them by its benzene rings in an η 2: η 2: η 2 fashion. As a result of such a type of the bonding, all carbon atoms of the benzene rings of PCP are involved in the coordination to the Lewis acidic Hg sites of the anticrown species. The synthesized 2 is the first example of a discrete, double-decker sandwich complex of macrocycle 1 with an aromatic hydrocarbon as well as the first complex of PCP in which both benzene rings of the PCP molecule are η 2: η 2: η 2 bonded to trimetal units.

Synthesis of new planar chiral [2.2]paracyclophane Schiff base ligands and their application in the asymmetric Henry reaction

A series of new planar and central chiral ligands based on [2.2]paracyclophane backbones were designed and prepared from enantiomerically pure 4-amino-13-bromo[2.2]paracyclophane and commercially available chiral amino alcohols. Their application in a copper-catalyzed asymmetric Henry reaction resulted in secondary alcohols with high yield and excellent selectivity for active aldehydes (up to 94% ee). This is a successful example of employing planar chiral [2.2]paracyclophane ligands in copper-catalyzed reaction.

Paracyclophanes as Versatile π-Donor Ligands Directing Formation of Extended Organometallic Networks

The coordination properties of multidentate nonplanar aromatic ligands containing two and three benzene rings, namely [2.2]- and [2.2.2]paracyclophanes, have been explored. A gas-phase deposition approach has been used to examine metal−π interactions in a solvent-free environment as well as to prepare organometallic π-complexes of paracyclophane ligands in crystalline form. To force bridging modes of paracyclophanes and to achieve the formation of extended organometallic assemblies, a dinuclear metal complex having two centers of Lewis acidity, namely [Rh2(O2CCF3)4], has been used. As a result, a product with Rh2:L2 = 1:1 composition (1) has been obtained from the reaction of dirhodium(II,II) tetrakis(trifluoroacetate) with [2.2]paracyclophane (L2 = C16H16). Complex 1 consists of alternating dimetal units and [2.2]paracyclophane bridges that form 1-D organometallic chains: [Rh2(O2CCF3)4·(μ2-η2:η2-C16H16)]1∞. In the case of [2.2.2]paracyclophane (L3 = C24H24), two new rhodium-based products of the stoichiometries Rh2:L3 = 1:2 (2) and 3:2 (3) have been prepared in crystalline form. Complex 2 is a discrete bis adduct with terminally bound aromatic ligands, [Rh2(O2CCF3)4·(η1-C24H24)2], while 3 exhibits a unique 2-D layered structure built on an unprecedented tridentate μ3-η2:η2:η2 coordination of [2.2.2]paracyclophane. Since the layers in 3 overlay to form [2.2.2]paracyclophane-based open channels running along the c direction, the gas sorption properties of the crystalline material, {[Rh2(O2CCF3)4]3·(C24H24)2}, have been tested. In addition to mono- and tridentate coordination of C24H24 revealed in 2 and 3, a rare bidentate bridging mode of [2.2.2]paracyclophane is found in its ruthenium(I) complex obtained by gas-phase reaction of hydrocarbon with the diruthenium(I,I) carbonyl trifluoroacetate unit, [Ru2(O2CCF3)2(CO)4]. The resulting product of the Ru2:L3 = 1:1 composition exhibits a 1-D chain structure, namely [Ru2(O2CCF3)2(CO)4·(μ2-η2:η2-C24H24)]1∞ (4). Overall, three new coordination modes of [2.2.2]paracyclophane have been revealed to afford a discrete complex, as well as 1-D and 2-D extended organometallic networks. This versatility of [2.2.2]paracyclophane has been fully realized under gas-phase deposition conditions that allow one to utilize effectively the geometrical and electronic structures of aromatic ligands in the formation of new organometallic products.

Cationic half-sandwich Ru(II) complexes bearing ( S)-2-pyridyl-imino-[2.2]paracyclophane ligands: Synthesis, intramolecular and interionic structure

( S)-2-Pyridyl-imino-[2.2]paracyclophane ligands 1 and 2 were synthesized by a condensation reaction of 2-COR-C 5H 4N ( 1: R = H; 2: R = Me) with enantiopure (−)- S-amino-[2.2]-paracyclophane. The reactions of 1 and 2 with [Ru(η 6-cymene)Cl(μ-Cl)] 2 afforded complexes [Ru(η 6-cymene)Cl(N,N)]X ( 3: N,N = 1; 4: N,N = 2; X - = BPh 4 - , PF 6 - , BF 4 - ) that were completely characterized in solution. For 4PF 6 the solid state structure was determined by X-ray single-crystal diffractometric studies. Two diastereoisomers [( S Ru, S L) and ( R Ru, S L)] were obtained in solution due to the presence of the planar chirality of paracyclophane (L) and the central chirality on ruthenium. 1H-NOESY NMR experiments were used to determine the chirality of the metal center and, consequently, to identify ( S Ru, S L) and ( R Ru, S L) diastereoisomers. The cymene orientation, obtained by intramolecular 1H-NOESY NMR investigations, and the relative anion–cation position, determined by interionic 1H-NOESY or 19F, 1H-HOESY NMR studies, depended on the nature of the diastereoisomer.

(μ-2,11-Dithia[3.3]paracyclophane-κ2S:S′)bis[(6-carboxypyridine-2-carboxylato-κ2N,O6)silver(I)]: a mixed-ligand silver-based dinuclear compound

In the title complex, [Ag2(C7H4NO4)2(C16H16S2)], each Ag(I) atom is trigonally coordinated by one S atom of a 2,11-dithia[3.3]paracyclophane (dtpcp) ligand, and by one N and one O atom of a 6-carboxypyridine-2-carboxylate ligand. Dtpcp acts as a bidentate ligand, bridging two inversion-related AgI atoms to give a dinuclear silver(I) compound. The dinuclear moieties are interconnected via O-H...O hydrogen bonds to form a two-dimensional zigzag sheet. Two such sheets are interwoven via pi-pi interactions between pyridine rings, affording an interwoven bilayer network.