Phenanthroline Nitrogen Research Articles

Chemical surface modification of carbon dots with Germanium: A highly sensitive and selective ratiometric fluorescence probe for Mg2+ detection using DFT and TD-DFT

In this study, we chemically modified carbon dots (Cdots) using germanium, enhancing their sensitivity and selectivity as a ratiometric fluorescence probe for precise detection of Mg2+ ions. Excitation of the modified Cdots resulted in a distinct emission peak at 527 nm, enabling accurate measurement of Mg2+ concentrations across a linear range. The surface modification with germanium led to the creation of novel emitting centers on the Cdots' surface. Theoretical calculations using density functional theory (DFT) revealed the effective suppression of these emitting centers through a photo-induced electron transfer (PET) process, utilizing the nitrogen lone pair electrons on the Cdots' surface. Furthermore, adjacent Cdots' surface pyrazino[2,3-f][1,10]-phenanthroline (PPT) nitrogen atoms formed chemical bonds with Mg2+ ions, resulting in the formation of aggregated Cdots. Consequently, the intricate complexation terminated the PET process, resulting in a novel emission peak at longer wavelengths. This study presents a highly sensitive and selective ratiometric fluorescent detection system with exceptional low concentration detection limit for precise Mg2+ ion detection.

Unusual lanthanoid contraction in crystal structures of 1,10-phenanthroline-2,9-diamides complexes with lanthanoid and yttrium trinitrates and the effect of chlorine substituents

Two series of crystal structures of 1:1 complexes of lanthanoid (excluding Pm) and yttrium trinitrates with N,N,N',N'-tetrabutylamide of 1,10-phenanthroline-2,9-dicarboxylic acid (L1) and N,N,N',N'-tetrabutylamide of 4,7-dichloro-1,10-phenanthroline-2,9-dicarboxylic acid (L2) that we started to study in previous works, have been completed. In all complexes, the ligands L1 and L2 coordinate central ions via two phenanthroline nitrogen atoms and two amide oxygen atoms. In complexes formed by early and middle lanthanoids, all three nitrate ions are bidentate, which gives a total coordination number equal to 10. In heavy lanthanoids complexes, starting from Ho for L1 and Yb for L2, coordination number was reduced to 9 because one nitrate turns to a monodentate coordination mode or is replaced by a water molecule. The Ln-N bonds in complexes with L2 are by 0.02–0.06 Å longer that those in L1 complexes throughout the whole lanthanoid row. With a decrease in the radius of the central ion, all coordination bonds become shorter, but their shortening occurs unevenly. In complexes with L1, between Dy and Ho, along with the reduction of the coordination number, the Ln(Y)–N bond lengths decrease abruptly, whereas the bonds Ln(Y)–O(NO3) shorten to a much lesser extent, and the Ln(Y)–O(amide) distances change almost continuously. In complexes with L2, a similar sharp shortening of Ln(Y)–N bonds takes place before the coordination number decreases to 9. The observed structural changes agree with the results of DFT calculations.

Phenanthrodiazaporphyrins: 1,10-Phenanthroline-Embedded Diazaporphyrin Analogues

Abstract A series of metal-free and metallo-diazaporphyrin analogues embedded with a 1,10-phenanthroline unit were synthesized and characterized. The molecular structure of the Ni(II) complex determined by single-crystal X-ray diffraction analysis confirmed its monocationic character in which the metal center adopts a typical square planar geometry binding with the pyrrole and phenanthroline nitrogen atoms. The spectroscopic and electrochemical studies, as well as molecular orbital calculations suggested that the metal complexes can be classified as 4nπ non-aromatic compounds.

Trifluoromethylated Phenanthroline Ligands Reduce Excited-State Distortion in Homoleptic Copper(I) Complexes.

We report the synthesis and excited-state dynamics for a series of homoleptic copper(I) trifluoromethylated phenanthroline complexes with two, three, and four trifluoromethyl functional groups. Our analysis of the steady-state absorbance and emission, transient-absorption spectroscopy, and electronic-structure-theory calculations results enable in-depth analysis of the pseudo-Jahn-Teller distortion inhibition from increased steric hindrance of the trifluoromethyl functional group relative to the prototypical dimethyl phenanthroline complex. Surprisingly, our results demonstrate that the greatest degree of pseudo-Jahn-Teller distortion inhibition is achieved with trifluoromethylation of only the 2 and 9 positions by an unusual combination of steric hindrance and stabilization of a nondistorted 1MLCT manifold observed by transient kinetic lifetimes and optimized excited-state structures. The intersystem-crossing (ISC) lifetime for the 2,9-bis(trifluoromethyl)-1,10-phenanthroline Cu(I) complex is 69 ps, while the triplet excited-state lifetime and emission quantum yield are 106 ns and 4 × 10-3, respectively. Further trifluoromethylation of the phenanthroline yields a greater σ bond inductive withdrawing force on the phenanthroline nitrogens, ultimately resulting in weaker coordination to the copper. Last, the surprising success of the 2,9-bis(trifluoromethyl)-1,10-phenanthroline Cu(I) complex by adjusting both ligand sterics and electronic properties outlines a new strategy for developing long-lived Cu(I) charge-transfer complexes.

Pamoic acid-phenanthroline co-crystal and its Cu(II) complex: X-ray structures and luminescence properties

In this study, pamoic acid-phenanthroline proton transfer complex [(HPhen)(HPam)] and its Cu(II) complex {[Cu(Phen)2(H2O)2]Pam·2.5H2O were prepared and characterized by spectroscopic and analytical methods. The structures of the compounds were determined by single crystal X-ray diffraction studies. In the structure of the proton transfer complex [(HPhen)(HPam)], one of the carboxyl group proton of a pamoic acid molecule transferred to the one of phenanthroline nitrogen atom. In the structure, no hydrogen bond contacts were observed between the protonated phenanthroline (HPhen)+ and mono-deprotonated pamoic acid (HPam)- and phenanthroline (HPhen)+ cations involve in a hydrogen bond (N1-H····O7) with a DMF solvate. Hydrogen bonds between mono-deprotonated pamoic acid [HPam]- anions and π-π stacking interactions play a crucial role in the packing of the structure. X-ray crystallographic data showed that the Cu(II) complex consists of [Cu(Phen)2(H2O)2]2+ cationic unit, a pamoate counter anion and lattice water molecules (2.5H2O per complex cation). In the structure, each Cu(II) ion are six-coordinated and bound to four nitrogen atoms of two phenanthroline ligands and two water ligands with a distorted octahedral geometry. The pamoate anion does not involve in coordination with Cu(II) ion. The cationic units are linked by intermolecular hydrogen bonds forming a 2D hydrogen bond network. 2D hydrogen bond network further extended to 3D network by π-π stacking interactions. Absorption and emission spectral features of the compounds were investigated both in the solid state and solution.

A luminescent europium metal–organic framework with free phenanthroline sites for highly selective and sensitive sensing of Cu2 + in aqueous solution

A luminescent europium metal–organic framework [Eu(HL)(L)(H2O)2]·2H2O (1) (H2L=(2,3-f)-pyrazino(1,10)phenanthroline-2,3-dicarboxylic acid) with uncoordinated phenanthroline nitrogen sites was hydrothermally synthesized. It exhibits highly sensitive and selective sensing of Cu2+ in aqueous solution. To the best of our knowledge, complex 1 is the first luminescent Eu-MOF with uncoordinated phenanthroline nitrogen sites for selective sensing of Cu2+ in aqueous solution. The probable sensing mechanism was discussed in detail.

Synthesis and Characterization of Homoleptic and Heteroleptic Cobalt, Nickel, Copper, Zinc and Cadmium Compounds with the 2‐(Tosylamino)‐N‐[2‐(tosylamino)benzylidene]aniline Ligand

AbstractThe electrochemical oxidation of anodic metal (cobalt, nickel, copper, zinc and cadmium) in an acetonitrile solution of the Schiff‐base ligand 2‐(tosylamino)‐N‐[2‐(tosylamino)benzylidene]aniline (H2L) afforded the homoleptic compounds [ML]. The addition of 1,1‐diphenylphosphanylmethane (dppm), 2,2′‐bipyridine (bipy) or 1,10‐phenanthroline (phen) to the electrolytic phase gave the heteroleptic complexes [NiL(dppm)], [ML(bipy)] and [ML(phen)]. The crystal structures of H2L (1), [NiL] (2), [CuL] (3), [NiL(dppm)] (4), [CoL(phen)] (5), [CuL(bipy)] (6) and [Zn(Lphen)] (7) were determined by X‐ray diffraction. The homoleptic compounds [NiL] and [CuL] are mononuclear with a distorted square planar [MN3O] geometry with the Schiff base acting as a dianionic (NamideNamideNimineOtosyl) tetradentate ligand. Both compounds exhibit an unusual π–π stacking interaction between a six‐membered chelate ring containing the metal and a phenylic ring of the ligand. In the heteroleptic complex [NiL(dppm)], the nickel atom is in a distorted tetrahedral [NiN3P] environment defined by the imine, two amide nitrogen atoms of the L2– dianionic tridentate ligand and one of the phosphorus atoms of the dppm molecule. In the other heteroleptic complexes, [CoL(phen)], [CuL(bipy)] and [ZnL(phen)], the metal atom is in a five‐coordinate environment defined by the imine, two amide nitrogen atoms of the dianionic tridentate ligand and the two bipyridine or phenanthroline nitrogen atoms. The compounds were characterized by microanalysis, IR and UV/Vis (Co, Ni and Cu complexes) spectroscopy, FAB mass spectrometry and 1H NMR ([NiL] and Zn and Cd complexes) and EPR spectroscopy (Cu complexes).

Dramatic improvement in catalyst loadings and molar ratios of coupling partners for Ni/Cr-mediated coupling reactions: heterobimetallic catalysts.

Two new ligands 1a,b are reported. Upon treatment with 1 equiv of NiCl(2) x (MeOCH(2))(2), 1a,b give the corresponding Ni complexes. X-ray analysis of 1a x NiCl(2) established that the NiCl(2) is selectively coordinated to the phenanthroline nitrogens. Ni/Cr heterobimetallic catalysts 1a,b x CrCl(2)/NiCl(2), prepared from 1a,b x NiCl(2), have been shown to behave exceptionally well in catalytic asymmetric Ni/Cr-mediated couplings, with highlights including the following: (1) 1-2 mol % catalyst is sufficient to complete the coupling; (2) only negligible amounts of the dimers, byproducts formed through the alkenyl Ni species, are observed; (3) the coupling goes to completion even with a 1:1 molar ratio of the coupling partners; and (4) the asymmetric induction is practically identical with that obtained from the coupling with the Cr catalysts prepared from (S)-sulfonamides 2a,b. The scope of the new Ni/Cr heterobimetallic catalysts was briefly studied using four additional aldehydes. The applicability of the new catalysts to polyfunctional substrates was demonstrated by two C-C bond formations chosen from the halichondrin/E7389 synthesis as examples.

Design, synthesis and evaluation of 4,7-diamino-1,10-phenanthroline G-quadruplex ligands

A series of 4,7-diamino-1,10-phenanthroline derivatives carrying positively charged side chains has been synthesized, and their G-quadruplex interaction evaluated by circular dichroism (CD) and surface plasmon resonance (SPR). In absence of side chains, 4,7-diamino-1,10-phenanthroline exhibits a weak but significant G-quadruplex stabilizing effect, compared to no stabilization by 1,10-phenanthroline. We hypothesize that this effect is due to increased basicity of the phenanthroline nitrogens and protonation or ion chelation to form a central positive charge which stack on the G-tetrad above the central ionic column. Introduction of positively charged side chains results in compounds with appreciable G-quadruplex stabilizing properties and high aqueous solubility, with the longer side chains giving more potent compounds. Ligands carrying guanidine side chains in general show higher quadruplex stabilizing activity and distinctly slower kinetic properties than their amino and dimethylamino analogues, possibly due to specific hydrogen bond interactions with the G-quadruplex loops.

Synthesis and Crystal Structure of Platinum Blue [(1,10-phen)Pt(μ-NHCOCH3)2Pt(1,10-phen)]2(NO3)4

The reaction of acetamide with PtphenCl2 gave a mixed-valence black-brown-colored platinum complex Ptphen(NHCOCH3)NO3 (I), which was studied by X-ray diffraction. The monoclinic crystal (a = 16.389(6) A, b = 19.664(6) A, c = 11.049(4) A; β = 122.8(3)°, V = 2993(18) A3, space group C2/m, Z = 4, R = 0.0432) is built of dimeric [Pt2phen2(NHCOCH3)2]2+ cations and NO32. anions. Each platinum atom in the dimer is linked to two nitrogen or oxygen atoms of the two bridging (NHCOCH3)− groups and two phenanthroline nitrogen atoms. The Pt-Pt distance in the dimer is 2.8891(19) A. In the crystal, the dimers form pairs (tetramers), the interdimer Pt…Pt distance being 3.167(2) A. Four platinum atoms are arranged nearly linearly (the Pt(2)Pt(1)Pt(1)* angle is 178.71(4)°). The UV-Vis spectrum of an aqueous solution of compound I exhibits bands at 360, 480, 630, 680, and 880 nm in the visible region. The diffuse reflectance spectrum of a polycrystalline sample of I (in the 300–900 nm range) contains bands at ∼360, ∼500, ∼600, ∼690, and ∼890 nm.

Mixed ligation to vanadium(III): Synthesis, spectra and structures of bis(acetylacetonato)( o-phenanthroline)vanadium(III) fluoroborate and bis(acetylacetonato)( o-phenanthroline)vanadium(III) perchlorate

Two mixed ligand vanadium(III) complexes bis(acetylacetonato)(phenanthroline)vanadium(III) fluoroborate ( 1) and bis(acetylacetonato)(phenanthroline)vanadium(III) perchorate ( 2) have been prepared and characterized by UV–Vis, IR, 1H NMR spectroscopic techniques and single crystal X-ray diffraction. The electronic spectra are as expected for V(III) in an octahedral environment. The 1H NMR spectra are typical of paramagnetic V(III) species. The complexes have crystallized with dichloromethane solvate and are isomorphous. The coordination sphere is composed of vanadium in a distorted octahedral environment, ligated to two bidentate chelating acetylacetonate ligands through the oxygen atoms and two phenanthroline nitrogens.

Sensitive Oxidation State Ambivalence in Unsymmetrical Three-Center (M/Q/M) Systems [(acac)2Ru(μ-Q)Ru(acac)2]n, Q = 1,10-Phenanthroline-5,6-dione or 1,10-Phenanthroline-5,6-diimine (n = +, 0, −, 2−)

The new redox systems [(acac)2 Ru(mu-Q1)Ru(acac)2](n) (1(n)) and [(acac)2 Ru(mu-Q2)Ru(acac)2](n) (2(n)) with Q1 = 1,10-phenanthroline-5,6-dione and Q2 = 1,10-phenanthroline-5,6-diimine were studied for n = +, 0, -, and 2- using UV-Vis-NIR spectroelectrochemistry and, in part, EPR and susceptometry. The ligands can bind the first metal (left) through the phenanthroline nitrogen atoms and the second metal (right) at the o-quinonoid chelate site. The neutral compounds are already different: Compound 1 is formulated as a Ru(II)(mu-Q1)*- Ru(III) species with partially coupled semiquinone and ruthenium(III) centers. In contrast, a Ru(III)(mu-Q2)2- Ru(III) structure is assigned to 2, which shows a weak antiferromagnetic spin-spin interaction (J = -1.14 cm(-1)) and displays an intense half-field signal in the EPR spectrum. The one-electron reduced forms are also differently formulated as Ru(II)(mu-Q1)2- Ru(III) for 1(-) with a Ru(III)-typical EPR response and as Ru(II)(mu-Q2)*- Ru(II) for 2(-) with a radical-type EPR signal at g = 2.0020. In contrast, both 1(2-) and 2(2-) can only be described as Ru(II)(mu-Q)2- Ru(II) species. The monooxidized forms 1(+) and 2(+) show very similar spectroscopy, including a Ru(III)-type EPR signal. Although no unambiguous assignment was possible here for the alternatives Ru(II)(mu-Q)0Ru(III), Ru(III)(mu-Q)2- Ru(IV) or Ru(III)(mu-Q)*- Ru(III), the last description is favored. The reasons for identical or different oxidation state combinations are discussed.

Synthesis of 2-pyridone-fused 2,2′-bipyridine derivatives. An unexpectedly complex solid state structure of 3,6-dimethyl-9H-4,5,9-triazaphenanthren-10-one

2-Pyridone-fused 2,2'-bipyridine derivatives and were synthesised. X-Ray diffraction analysis of revealed a highly complex solid state structure with a disordered molecule imbedded in a channel structure formed by a centrosymmetric lattice of hexagonally packed, hydrogen bonded columns. The columns are assembled from three symmetry independent molecules. Dimerisation of the self-complementary cis-amide hydrogen bond motif is overridden by the fulfilment of the proton coordination ability of the phenanthroline nitrogens in accordance with Etter's rules of hydrogen bond priorities.

Crystallography and luminescence of divalent osmium complexes green osmium emitters and possible evidence for d-orbital backbonding

The preparation, photophysics, and solid-state structures of three osmium cored complexes are reported. The osmium complexes take the general form of [OsCl(N–N)(L–L)(CO)]+ hexafluorophosphate where N stands for a derivative of 1,10-phenanthroline and L stands for a phosphine type ligand. The emission of the complexes is shown to be blue shifted to the osmium emission of Os(bpy)32+. The emissions of the various complexes range from yellow (560 nm) to yellow-green (550 nm) to green (520 nm). The quantum yields vary between 60% and 75%. The complexes show lifetimes that are much longer than expected with ranges of 6.5–38 μs. Crystallographic results show that the carbonyl is trans to a phenanthroline nitrogen and the chloro ligand is trans to phosphorus. A discussion will be presented as to the nature of the bonding in these complexes based upon the data from the crystallography.

Coordination properties of new bis(1,4,7-triazacyclononane) ligands: a highly active dizinc complex in phosphate diester hydrolysis.

The synthesis and characterization of three new bis([9]aneN(3)) ligands, containing respectively 2,2'-bipyridine (L(1)), 1,10-phenanthroline (L(2)), and quinoxaline (L(3)) moieties linking the two macrocyclic units, are reported. Proton binding and Cu(II), Zn(II), Cd(II), and Pb(II) coordination with L(1)-L(3) have been studied by potentiometric titrations and, for L(1) and L(2), by spectrophotometric UV-vis measurements in aqueous solutions. All ligands can give stable mono- and dinuclear complexes. In the case of L(1), trinuclear Cu(II) complexes are also formed. The stability constants and structural features of the formed complexes are strongly affected by the different architecture and binding properties of the spacers bridging the two [9]aneN(3) units. In the case of the L(1) and L(2) mononuclear complexes, the metal is coordinated by the three donors of one [9]aneN(3) moiety; in the [ML(2)](2+) complexes, however, the phenanthroline nitrogens are also involved in metal binding. Finally, in the [ML(3)](2+) complexes both macrocyclic units, at a short distance from each other, can be involved in metal coordination, giving rise to sandwich complexes. In the binuclear complexes each metal ion is generally coordinated by one [9]aneN(3) unit. In L(1), however, the dipyridine nitrogens can also act as a potential binding site for metals. The dinuclear complexes show a marked tendency to form mono-, di-, and, in some cases, trihydroxo species in aqueous solutions. The resulting M-OH functions may behave as nucleophiles in hydrolytic reactions. The hydrolysis rate of bis(p-nitrophenyl)phosphate (BNPP) was measured in aqueous solution at 308.1 K in the presence of the L(2) and L(3) dinuclear Zn(II) complexes. Both the L(2) complexes [Zn(2)L(2)(OH)(2)](2+) and [Zn(2)L(2)(OH)(3)](+) and the L(3) complex [Zn(2)L(3)(OH)(3)](+) promote BNPP hydrolysis. The [Zn(2)L(3)(OH)(3)](+) complex is ca. 2 orders of magnitude more active than the L(2) complexes, due both to the short distance between the metal centers in [Zn(2)L(3)(OH)(3)](+), which could allow a bridging interaction of the phosphate ester, and to the simultaneous presence of single-metal bound nucleophilic Zn-OH functions. These structural features are substantially corroborated by semiempirical PM3 calculations carried out on the mono-, di-, and trihydroxo species of the L(3) dizinc complex.

Model investigations for vanadium-protein interactions: vanadium(III) compounds with dipeptides and their oxovanadium(IV) analogues

The reaction of VCl(3) with 1,10-phenanthroline and a series of dipeptides (H(2)dip), having aliphatic as well as aromatic side chains, in methyl alcohol and in the presence of triethylamine affords vanadium(III) compounds of the general formula [V(III)(dip)(MeOH)(phen)]Cl. Aerial oxidation/hydrolysis of the vanadium(III) species gives their oxovanadium(IV) analogues of the general formula [V(IV)O(dip)(phen)]. X-ray crystallographic characterization of the [V(IV)O(dip)(phen)] compounds (where dip(2-)=Gly- L-Ala, Gly- L-Val and Gly- L-Phe) revealed that the vanadium atom possesses a severely distorted octahedral coordination and is ligated to a tridentate dip(2-) ligand at the N(amine) atom, the deprotonated N(peptide) atom and one of the O(carboxylate) atoms, as well as an oxo group and two phenanthroline nitrogen atoms. Circular dichroism characterization of the V(III)/V(IV)O(2+)-dipeptide compounds revealed a strong signal for the V(IV)O(2+) species in the visible range of the spectrum, with a characteristic pattern which may be exploited to identify the N(am), N(pep) and O(car) ligation of a peptide or a protein to V(IV)O(2+) center, and a weak Cotton effect of opposite sign to their vanadium(III) analogues. The visible spectra of the V(III)-dipeptide compounds revealed two d-d bands with high intensity, thus indicating that the covalency of the metal-donor atoms is significant, i.e. the vanadium d orbitals are significantly mixed with the ligand orbitals, and this is confirmed by the low values of their Racah B parameters. The high-intensity band of the V(IV)O(2+)-dipeptide compounds at approximately 460 nm implies also a strong covalency of the metal with the equatorial donor atoms and this was supported by the EPR spectra of these compounds. Moreover, the V(III)/V(IV)O(2+)-dipeptide complexes were characterized by EPR and IR spectroscopies as well as conductivity and magnetic susceptibility measurements.

Metal Ion Catalysis in the Hydrolysis of Esters of 2-Hydroxy-1,10-phenanthroline: The Effects of Metal Ions on Intramolecular Carboxyl Group Participation

Rate constants have been determined for hydrolysis of the acetate, glutarate, and phthalate monoesters of 2-hydroxy-1,10-phenanthroline in water at 30°C and μ = 0.1 M with KCl. The hydrolysis reactions of the esters are hydroxide ion catalyzed at pH > 9. The phthalate and glutarate monoesters have in addition pH-independent reactions from pH 5.5 to 9 that involve intramolecular participation by the neighboring carboxylate anion. The pH-independent reaction of the glutarate monoester is ∼5-fold faster than that of the phthalate monoester. The plots of log kobsd vs pH for hydrolysis of the carboxyl substituted esters are bell shaped at pH < 5, which indicates a rapid reaction of the zwitterionic species (carboxyl anion and protonated phenanthroline nitrogen). The divalent metal ions, Cu2+, Ni2+, Zn2+, and Co2+, complex strongly with the esters; saturation occurs at metal ion concentrations less than 0.01 M. The 1:1 metal ion complexes have greatly enhanced rates of hydrolysis; the second-order rate constants for the OH− reactions are increased by factors of 105 to 108 by the metal ion. The pH-rate constant profiles for the phthalate and glutarate ester metal ion complexes have a sigmoidal region below pH 6 that can be attributed to a metal ion-promoted carboxylate anion nucleophilic reaction. The carboxyl group reactions are enhanced 102 - to 103 -fold by the metal ions, which allows the neighboring group reaction to be competitive with the favorable metal ion-promoted OH− reaction at pH < 6, but not at pH > 6. The half-lives of the pH-independent neighboring carboxyl group reactions of the Cu(II) complexes at 30°C are ∼l2 s. The other metal ion complexes are only slightly less reactive (half-lives vary from 2.5 to 40 s). These are the most rapid neighboring carboxyl group reactions that have been observed in ester hydrolysis.

Synthesis and Biological Activity of Manganese (II) Complexes of Phthalic and Isophthalic Acid: X‐Ray Crystal Structures of [Mn(ph)(Phen)2(H2O)]· 4H2O, [Mn(Phen)2(H2O)2]2(Isoph)2(Phen)· 12H2O and {[Mn(Isoph)(bipy)]4· 2.75biby}n(phH2 = Phthalic Acid; isoph = Isophthalic Acid; phen = 1,10‐Phenanthroline; bipy = 2,2‐Bipyridine)

Manganese(II) acetate reacts with phthalic acid (phH2) to give [Mn(ph)]·0.5H2O (1). Reaction of 1 with 1,10-phenanthroline produces [Mn(ph)(phen)]·2H2O (2) and [Mn(ph)(phen)2(H2O)]·4H2O (3). Reaction of isophthalic acid (isophH2) with manganese(II) acetate results in the formation of [Mn(isoph)]·2H2O (4). The addition of the N,N-donor ligands 1,10-phenanthroline or 2,2'-bipyridine to 4 leads to the formation of [Mn2 (isoph)2(phen)3)]·4H2O (5), [(Mn(phen)2(H2O)2]2(isoph)2(phen)·12H2O (6) and {[Mn(isoph)(bipy)]4·2.75 biby}n (7), respectively. Molecular structures of 3, 6 and 7 were determined crystallographically. In 3 the phthalate ligand is bound to the manganese via just one of its carboxylate groups in a monodentate mode with the remaining coordination sites filled by four phenanthroline nitrogen and one water oxygen atoms. In 6 the isophthalates are uncoordinated with the octahedral manganese center ligated by two phenanthrolines and two waters. In 7 the Isophthalate ligands act as bridges resulting in a polymeric structure. One of the carboxylate groups is chelating a single manganese with the other binding two metal centres in a bridging bidentate mode. The phthalate and isophthalate complexes, the metal free ligands and a number of simple manganes salts were each tested for their ability, to inhibit the growth of Candida albicans. Only the “metal free” 1,10-phenanthroline and its manganese complexes were found to be active.

Effect of Protonation and Zn(II) Coordination on the Fluorescence Emission of a Phenanthroline-Containing Macrocycle. An Unusual Case of “Nonemissive” Zn(II) Complex

Ligand 2,5,8-triaza[9]-10,23-phenanthrolinophane (L) contains a triamine chain connecting the 2,9 positions of a phenanthroline unit. Protonation of L has been studied by means of potentiometric and 1H and 13C NMR techniques, allowing the determination of the basicity constants and of the stepwise protonation sites. Protonation strongly affects the fluorescence emission properties of the chemosensor L. The two benzylic amine groups, namely, the two aliphatic amine groups adjacent to phenanthroline, are the most efficient nitrogens in fluorescence emission quenching. In the diprotonated receptor [H2L]2+ both of these nitrogens are protonated, and therefore this species is the most emissive. In the [H3L]3+ species the three acidic protons are located on the amine groups of the polyamine chain. This species is still emissive, but less so than [H2L]2+, due to formation of a hydrogen bond network involving the phenanthroline nitrogens, as shown by the crystal structure of the [H3L]Br3·H2O salt. A potentiometri...

Electrochemical synthesis of nickel(II) complexes of tosylamides: crystal structures of [(4-methylphenyl)sulfonyl]-imino-1H-pyridine], 2,2′-bipyridine bis{[(4-methylphenyl) sulfonyl]-2-pyridyl-amide}nickel(II) and 1,10-phenanthroline bis{[(4-methylphenyl) sulfonyl]-2-pyridyl-amide}nickel(II)

The complex [NiL 2] has been synthesised by the electrochemical oxidation of nickel in an acetonitrile solution of [(4-methylphenyl)sulfonyl]-imino-1H-pyridine (HL). When the oxidation was carried out in the presence of neutral ligands L′ (pyridine, 2,2′-bipyridine or 1,10-phenanthroline) the complexes [NiL 2py 2], [NiL 2bipy] and [NiL 2phen] were obtained. The crystal structures of [(4-methylphenyl)sulfonyl]-imino-1H-pyridine, 2,2′-bipyridine bis{[(4-methylphenyl)sulfonyl]-2-pyridyl-amide}nickel(II) and 1,10-phenanthroline bis{[(4-methylphenyl) sulfonyl]-2-pyridyl-amide}nickel(II) were determined by X-ray diffraction methods. In the monomeric complexes, the nickel atom is in a distorted octahedral environment defined by the amide and pyridyl nitrogen atoms of the two ligands and the two bipyridine or phenanthroline nitrogen atoms. The vibrational and electronic spectra of the complexes are discussed and are shown to agree with the structures.