Phen Unit Research Articles

Conformational Solvatomorphism in a [2]Catenane

The combination of a flexible pyridine-appended ligand (L1) with 4,4′-bipyridine (L2) and cis-protected Pd(II) units, Pd(L′)(NO3)2, in water yielded a concentration-dependent equilibrium mixture of the corresponding [2]catenanes [Pd2(L′)2(L1)(L2)]2(NO3)8 and their constituent macrocycles [Pd2(L′)2(L1)(L2)](NO3)4. The cis-protecting units (L′) used were ethylenediamine (en), tetramethylethylenediamine (tmeda), 2,2′-bipyridine (bpy), and 1,10-phenanthroline (phen). Crystallization of the [2]catenanes via slow evaporation of their CH3CN/H2O (1:1) solutions yielded a single crystalline form in the case of [Pd2(2,2′-bpy)2(L1)(L2)]2(NO3)8 and two concomitant crystalline forms (solvates) in the case of [Pd2(phen)2(L1)(L2)]2(NO3)8. The formation of the [2]catenane is facilitated by noncovalent interactions such as N–H···O, C–H···O, and C–H···π contacts and π···π stacking. The solvates of [Pd2(phen)2(L1)(L2)]2(NO3)8 revealed differences in the orientation of the amide carbonyl group and conformational differences in the ligands and phen units in the macrocycles and may thus be termed conformational solvatomorphs. The molecular packing in all the structures was found to be driven by intermolecular π···π stacking interactions between the aromatic rings in their cis-protected Pd(II) units. However, because of the awkward shape of the molecules, the closest 2,2′-bpy and phen units in all the structures overlap differently rather than the commonly observed “head-to-tail” or “head-to-head” modes.

Heteronuclear d-d and d-f Ru(ii)/M complexes [M = Gd(iii), Yb(iii), Nd(iii), Zn(ii) or Mn(ii)] of ligands combining phenanthroline and aminocarboxylate binding sites: combined relaxivity, cell imaging and photophysical studies.

A ligand skeleton combining a 1,10-phenanthroline (phen) binding site and one or two heptadentate N3O4 aminocarboxylate binding sites, connected via alkyne spacers to the phen C3 or C3/C8 positions, has been used to prepare a range of heteronuclear Ru·M and Ru·M2 complexes which have been evaluated for their cell imaging, relaxivity, and photophysical properties. In all cases the phen unit is bound to a {Ru(bipy)2}2+ unit to give a phosphorescent {Ru(bipy)2(phen)}2+ luminophore, and the pendant aminocarboxylate sites are occupied by a secondary metal ion M which is either a lanthanide [Gd(iii), Nd(iii), Yb(iii)] or another d-block ion [Zn(ii), Mn(ii)]. When M = Gd(iii) or Mn(ii) these ions provide the complexes with a high relaxivity for water; in the case of Ru·Gd and Ru·Gd2 the combination of high water relaxivity and 3MLCT phosphorescence from the Ru(ii) unit provides the possibility of two different types of imaging modality in a single molecular probe. In the case of Ru·Mn and Ru·Mn2 the Ru(ii)-based phosphorescence is substantially reduced compared to the control complexes Ru·Zn and Ru·Zn2 due to the quenching effect of the Mn(ii) centres. Ultrafast transient absorption spectroscopy studies on Ru·Mn (and Ru·Zn as a non-quenched control) reveal the occurrence of fast (<1 ns) PET in Ru·Mn, from the Mn(ii) ion to the Ru(ii)-based 3MLCT state, i.e. MnII-(phen˙-)-RuIII → MnIII-(phen˙-)-RuII; the resulting MnIII-(phen˙-) state decays with τ ≈ 5 ns and is non-luminescent. This occurs in conformers when an ET pathway is facilitated by a planar, conjugated bridging ligand conformation connecting the two units across the alkyne bridge but does not occur in conformers where the two units are electronically decoupled by a twisted conformation of the bridging ligand. Computational studies (DFT) on Ru·Mn confirmed both the occurrence of the PET quenching pathway and its dependence on molecular conformation. In the complexes Ru·Ln and Ru·Ln2 (Ln = Nd, Yb), sensitised near-infrared luminescence from Nd(iii) or Yb(iii) is observed following photoinduced energy-transfer from the Ru(ii) core, with Ru → Nd energy-transfer being faster than Ru → Yb energy-transfer due to the higher density of energy-accepting states on Nd(iii).

Copper(II) Complexes of Phenanthroline and Histidine Containing Ligands: Synthesis, Characterization and Evaluation of their DNA Cleavage and Cytotoxic Activity.

Copper(II) complexes have been intensely investigated in a variety of diseases and pathological conditions due to their therapeutic potential. The development of these complexes requires a good knowledge of metal coordination chemistry and ligand design to control species distribution in solution and tailor the copper(II) centers in the right environment for the desired biological activity. Herein we present the synthesis and characterization of two ligands HL1 and H2L2 containing a phenanthroline unit (phen) attached to the amino group of histidine (His). Their copper(II) coordination properties were studied using potentiometry, spectroscopy techniques (UV-vis and EPR), mass spectrometry (ESI-MS) and DFT calculations. The data showed the formation of single copper complexes, [CuL1]+ and [CuL2], with high stability within a large pH range (from 3.0 to 9.0 for [CuL1]+ and from 4.5 to 10.0 for [CuL2]). In both complexes the Cu2+ ion is bound to the phen unit, the imidazole ring and the deprotonated amide group, and displays a distorted square pyramidal geometry as confirmed by single crystal X-ray crystallography. Interestingly, despite having similar structures, these copper complexes show different redox potentials, DNA cleavage properties and cytotoxic activity against different cancer cell lines (human ovarian (A2780), its cisplatin-resistant variant (A2780cisR) and human breast (MCF7) cancer cell lines). The [CuL2] complex has lower reduction potential (Epc= -0.722 V vs -0.452 V for [CuL1]+) but higher biological activity. These results highlight the effect of different pendant functional groups (carboxylate vs amide), placed out of the coordination sphere, in the properties of these copper complexes.

Role of peripheral phenanthroline groups in the self-assembly of self-assembled molecular triangles

Self-assembled molecular triangles [Pd3(phen)3(imidazolate)3](NO3)3, 1a and [Pd3(phen)3 (imidazolate)3](PF6)3, 1b are prepared by the combination of imidazole with Pd(phen)(NO3)2 and Pd(phen) (PF6)2, respectively. Imidazole was deprotonated during the complexation reactions and the imidazolate so formed acted as a bis-monodentate bridging ligand to form the bowl-shaped trinuclear architectures of 1a/b. Relative orientation of the imidazolate moieties can be best described as syn,anti,antias observed in the crystal structure of 1b. However, in solution state, slow conformational changes are assumed on the basis of 1HNMR spectral data. The molecular triangles are crafted with three peripheral phen units capable of π−π stacking interactions. Well-fashioned intermolecular π−π interactions are observed in the solid-state, wherein further self-assembly of already self-assembled triangle is observed. Self-assembly of the self-assembled molecular triangle [Pd3(phen)3(imidazolate)3](PF6)3 is observed in the solid-state where the triangular panels are packed by utilizing intermolecular π−π interactions in a chain like fashion.

Syntheses, Structures, and Characterization of Two New Complexes Constructed From Asymmetric Ferrocenyldicarboxylate Ligand

Asymmetric ligand 1′-(formyl)ferrocene-1-succinic acid and two new complexes, {[Pb(η 2-OOCFcCOC2H4COO-η 2)(phen)]2 (CH3OH)} (1), {[Zn(η 2 -OOCFcCOC2H4COO-η 2)(phen)]2 (CH3OH)(H2O)} (2) [Fc = (η 5-C5H4)Fe(η 5-C5H4), phen = 1,10-phenanthroline] have been synthesized and characterized. Single-crystal X-ray crystallographic analyses reveal that both complexes 1 and 2 present dimeric structures coordinated by carboxyl groups and phen units. Interestingly, various π···π interactions or Pb···π interactions are discovered, which extend the two dimers to infinite 3-D supramolecular networks. Furthermore, the thermal analyses results are in reasonable agreement with the crystal structure analyses of complexes 1 and 2.

Variation of cis/trans configuration of 3,8-dithiophen and 3,8-di-3-methylthiophen-substituted 1,10-phenanthroline in their cadmium(II) nitrate complexes originating from substituent and anionic effects

A pair of 3,8-dithiophen (dtphen) and 3,8-di-3-methylthiophen (dmtphen) substituted 1,10-phenanthroline cadmium(II) nitrates, formulated as [Cd(dmtphen)2(NO3)2] (1) and [Cd(dtphen)2(NO3)2] (2), exhibit cis and trans configuration in the whole complexes because of the substituent effects of methyl group in the dmtphen ligand. In 1 and 2, both ligands possess similar cis/trans configuration but different dihedral angles from 19.0(1)° to 45.5(1)° in 1 and 2.6(1)° to 5.9(1)° in 2 due to the spatial crowding effects of methyl group. Additionally, anionic effects of NO3−, Cl−, and Br− have been studied where two cis Cd(II) complexes formulated as [CdBr2(dmtphen)2] (3) and [CdCl2(dtphen)] (4) are obtained and the side thiophene and methyl-thiophene rings in each ligand adopt the cis/trans and trans/trans configuration relative to the central phen unit.

Mixed-1,10-phenanthroline–Cu(II) complexes: Synthesis, cytotoxic activity versus hematological and solid tumor cells and complex formation equilibria with glutathione

Cu(II) complexes with 1,10-orthophenanthroline (phen) show cytotoxic and antitumoral effects. To enhance and exploit these features, we studied complexes containing one or two phen units together with N,N′-substituted-imidazolidine-2-thione (L). We synthesized and structurally characterized the precursor molecule Cu(phen)(OH2)2(OClO3)2, and determined the complex formation constants of [Cu(phen)(L)]2+. We studied the cytotoxic activity of [Cu(phen)2(L)](ClO4)2 versus human hematologic (CCRF-CEM and CCRF-SB) and solid tumor-derived cell lines (K-MES-1, DU-145). The cytotoxic activities, in the 1–3μM range, show that our Cu(II)–complexes possess comparable inhibitory activities against both leukemia and carcinoma cells, unlike the majority of antineoplastic agents, usually more potent against hematologic cancer cells than against solid tumor cells. Because the free Cu(II) ion is reduced by glutathione (GSH), we studied the reactivity of our complexes with GSH, providing evidence that no redox reaction occurred under the chosen experimental conditions. Complex formation equilibria were present, studied by spectrophotometric titrations. The redox properties of the prepared compounds were also investigated by cyclic voltammetry, confirming that the mixed Cu(II) complexes were resistant to reduction.

Transition‐Metal‐Complexed Cyclic [3]‐ and [4]Pseudorotaxanes Containing Rigid Ring‐and‐Filament Conjugates: Synthesis and Solution Studies

By using the "gathering-and-threading" effect of copper(I) with rigid ring-and-string conjugates, daisy-chain-type [3]- and [4]pseudorotaxanes could be prepared in high yields. The organic fragment used consisted of a 2,9-diphenyl-1,10-phenanthroline (dpp)-containing ring attached to a coordinating filament capable of threading through the ring of another molecule by coordination to copper(I). The bidentate chelate introduced in the axis was also a 1,10-phenanthroline (phen) derivative with two methyl groups ortho to the nitrogen atoms of the phen unit. The organic component was prepared following a multistep strategy, one of the key steps being the attachment of the ring to the lateral axis. This connection was done by a condensation reaction between an ortho dione located at the back of a ring-incorporated phen and an aromatic aldehyde, which was the end-function of the thread. An oxazole nucleus was obtained after the condensation, which provided a rigid connection between the ring and the axis. In this way, the coordination axes of the ring-incorporated bidentate chelate and of the ligand belonging to the lateral filament were approximately orthogonal to one another. The design was such that the tetrameric complex, a [4]pseudorotaxane, seemed to be the most stable species, owing to the mutual geometrical arrangement of the filament and the ring. Various spectroscopic techniques, such as (1)H NMR spectroscopy, including DOSY, and electrospray ionization mass spectroscopy (ESI-MS), clearly demonstrated that a mixture of cyclic [3]- and [4]pseudorotaxane was obtained; the proportions of both components depended on concentration and temperature. Copper(I) was not the only metal center leading to the formation of cyclic pseudorotaxanes. A similar effect was observed with silver(I) as the templating metal: quantitative formation of threaded species was observed, with a higher proportion of trimer over tetramer than in the copper(I) case. Concentration and temperature effects were investigated for both series of Cu(I) - and Ag(I) -complexed threaded species showing that formation of the trimer was favored upon dilution or heating of the solution.

Synthesis and ion-sensing phenomena of two new helical conjugated oligomers containing 1,10-phenanthroline and oligo-alkylthiophene

Two new 1,10-phenanthroline (Phen) containing conjugated oligomers, oligo-3,8-bis(4-octylthiophene-2-yl)-1,10-phenanthroline) (PDTPh) and oligo-3,8-bis-(4-octyl-5-(4-ctylthiophene-2-yl)thiophene-2-yl)-1,10-phenanthroline) (PTTPh), as well as their corresponding monomers (OTPhOT and OTOTPhOTOT) were prepared and their metal ion-sensing properties were investigated. The oligomers showed high thermal stability, good proccessibility, and gave varied color when reacted with different metal ions. Oligomers also showed distinct responses toward metal ions when compared with their corresponding monomers, suggesting that the ionochromic responses were determined by not only the coordinating ability of Phen unit but also the conformation of oligomer chains. Moreover, the differences in the ion-sensing behaviors between OTPhOT and OTOTPhOTOT also suggested that the coordination ability of Phen depends on its substituents. The oligo-alkylthiophene moieties in PDTPh and PTTPh acted as spacers to reorganize the conformation of the oligomer chains, as well as the electron donating groups to adjust the coordination ability of the Phen. These findings provide a clue for designing Phen-containing ion-sensors for specified ion-sensing applications. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 1586–1597, 2008

Fluorescence quenching effect of metal ions for α,α′-diamine containing conjugated polymers in solid films

The fluorescence quenching effect of the conjugated polymers P1 and P2 (the molecular recognitions are twisted 2,2′-bipyridine (bpy) and planar 1,10-phenanthrolin (phen), respectively) films upon the addition of metal ions has been studied. And the results showed that P2 exhibited stronger fluorescence quenching ability upon the addition of both transition metal ions and main group metal ions compared with that of P1. The 20° twist angle between the two consecutive pyridine rings of bpy unit in the P1 main chain is the reason for the weaker fluorescence quenching ability compared with P2, in which the planar phen unit can chelate with metal ions relatively freely without the conformational transition. So P2 is a kind of material with better properties for solid film devices, such as sensors for metal ions recognition.

Highly luminescent Eu(3+) and Tb(3+) macrocyclic complexes bearing an appended phenanthroline chromophore.

A two-component ligand system (1) containing 1,4,7,10-tetraazacyclododecane-1,4,7-triacetic acid (DO3A) as the hosting unit for the lanthanide cations and an appended asymmetrically functionalized 1,10-phenanthroline (phen) as the chromophore was synthesized. The 1:1 complexes with Eu(3+), Gd(3+), Tb(3+), and Yb(3+) have been prepared and studied in aqueous solution. For Gd.1, a relaxivity value of 2.4 mM(-1) s(-1) has been measured at 20 MHz and 25 degrees C, which indicates that there are no water molecules in the first coordination sphere of the metal ion. The analysis of high resolution (1)H NMR spectra of Yb.1 supports this view and suggests the direct involvement of the phen moiety in the coordination of the metal ion. For Eu.1 and Tb.1, the absorption and luminescence spectra, the overall luminescence efficiencies, and the metal-centered (MC) lifetimes were obtained; coordination features were also determined by comparing luminescence properties in water and deuterated water. For Eu.1 and Tb.1, the overall emission sensitization (se) process in air-equilibrated water was found to be notably effective with phi(se) = 0.21 and 0.11, respectively. A detailed study of the steps originating from light absorption at the phen unit and leading to MC sensitized emission was performed.

Disulfide- and thiol-incorporating copper catenanes: synthesis, deposition onto gold, and surface studies.

Two new copper-complexed [2]catenanes have been prepared, both of which consist of two different interlocking rings. In both cases, one of the rings incorporates a disulfide bridge. The other ring contains either a single chelate (phen=1,10-phenanthroline, a bidentate ligand) or two different chelates (phen and terpy, 2,2',6',2"-terpyridine, a tridentate chelate). Deposition of these two complexes on a gold electrode surface was carried out by standard procedures, leading to reductive cleavage of the S-S bridge. The adsorbed species can be viewed as [2]catenanes for which the gold atoms of the electrode surface are an integral fragment of one of the two rings. They yield clear electrochemical responses, but no motion is observed for the catenane incorporating a phen unit and a terpy fragment in one of the two rings, regardless of the metal oxidation state. This is at odds with the behavior of the parent compound in solution, which undergoes ring-gliding motions upon electrochemical reduction or oxidation of the copper center. Near-field microscopy was used to study the deposited layers (STM and AFM). STM images suggest that the molecules do not tend to order at long range on the surface. Polarization modulation-infrared reflection absorption spectroscopy (PM-IRRAS) led to promising results: the two catenanes deposited are likely to be oriented perpendicular to the gold surface. Supporting information for this article is available on the WWW under http://www.wiley-vch.de/contents/jc_2111/2002/f3636_s.pdf or from the author. 1: Infrared spectra of [Cu.2]+ as a powder (black line, transmission IR spectroscopy) and as a SAM on gold (dotted line, PM-IRRAS). (Spectra offset and scaled for clarity; significant peaks marked with an asterisk.) 2: STM image (819x819 nm2) of a monolayer of [Cu.3]+ on Au(111) on mica.

Synthesis and Luminescent Properties of Novel Silicon-based Electroluminescent Copolymers with Ruthenium(II)-Chelated Complexes

A new class of silicon-based alternating copolymers having Ruthenium(II)-chelated complexes was synthesized to use as electroluminescent materials by Heck reaction between organosilicon divinyl monomers and Ru(II)-chelated monomers. The incorporation of organosilicon units with the aromatic or aliphatic groups on the silicon atoms into ®-conjugated systems improved their processability and interrupted the ®-conjugation length. The maximum absorption wavelength (λmax) of a non-chelated polymer (SiHMPhen) containing a phenanthroline (Phen) unit exhibited one strong bands at 305 nm for Phen units and a moderate peak around 350 nm for π-conjugated backbones. With an excitation wavelength of 360 nm, the PL spectrum of SiHMPhen exhibits a strong band at 420 nm in the blue region. Ru(II)-chelated copolymers showed strong absorption bands around 386–392 nm. Upon a photoexcitation with 400 nm, their PL spectra show a strong band at 430 nm in the blue region. The Ru(II)-chelated copolymers were thermally stable up to 300°C in air.