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PubMedDate not supplied

DNA binding of iron(II) mixed-ligand complexes containing 1,10-phenanthroline and 4,7-diphenyl-1,10-phenanthroline.

Absorption spectroscopy and circular dichroism (CD) have been used to characterize the DNA binding of [Fe(phen)3]2+, [Fe(phen)2(DIP)]2+ and [Fe(phen)(DIP)2]2+ where phen and DIP stand for 1,10-phenanthroline and 4,7-diphenyl-1,10-phenanthroline, respectively. Both [Fe(phen)3]2+ and [Fe(phen)2(DIP)]2+ bind weakly to calf thymus DNA (CT-DNA) in an electrostatic mode, while [Fe(phen)(DIP)2]2+ binds more strongly to CT-DNA, possibly in an intercalation mode. The hypochromicity, red shift and Kb increase in the order [Fe(phen)3]2+ < [Fe(phen)2(DIP)]2+ < [Fe(phen)(DIP)2]2+ in accordance with the increase in size and hydrophobicity of the iron(II) complexes. The thermodynamic parameters obtained suggest that the DNA binding of both [Fe(phen)3]2+ and [Fe(phen)2(DIP)]2+ is entropically driven, while that of [Fe(phen)(DIP)2]2+ is enthalpically driven. A strong CD spectrum in the UV and visible region develops upon addition of CT-DNA into the racemate solution of each iron(II) complex (Pfeiffer effect). This has revealed that a shift in diastereomeric inversion equilibrium takes place in the solution to yield an excess of one of the DNA-complex diastereomers. The striking resemblance of the CD spectral profiles to those of the pure delta-enantiomer indicates that the delta-enantiomer of the iron(II) complexes is preferentially bound to CT-DNA. The mechanism of the development of Pfeiffer CD is proposed on the basis of kinetic studies on the DNA binding of the racemic iron(II) complexes.

Circular Dichroism↗
PubMed2006

DNA interaction of platinum(II) complexes with 1,10-phenanthroline and extended phenanthrolines.

The interaction with DNA of the platinum(II) square planar complexes [Pt(N-N)(py)(2)](2+) (N-N = 1,10-phenanthroline (phen), dipyrido[3,2-d:2',3'-f]quinoxaline (dpq), dipyrido[3,2-a:2',3'-c]phenazine (dppz), benzodipyrido[b:3,2-h:2'3'-f]phenazine (bdppz)) has been investigated by means of absorption, circular and linear dichroism spectroscopy, DNA melting, and viscosity. In the presence of excess [DNA] all the complexes intercalate to the double helix. For those with the most extended phenanthrolines the binding mode depends on the [DNA]/[complex] ratio (q); at low q values the substances bind externally to DNA probably self-aggregating along the double helix. When the DNA concentration is large enough, the aggregate breaks up and the complex intercalates within the nucleobases. The complexes self-aggregate, without added DNA, in the presence of a large salt concentration.

DNA↗
PubMed2006

Ruthenium-cluster-mediated activation of all bonds of a methyl group of 6,6'-dimethyl-2,2'-bipyridine and 2,9-dimethyl-1,10-phenanthroline: transformation of the latter into a 2-alkenyl-9-methyl-1,10-phenanthroline ligand.

The treatment of [Ru3(CO)12] with 6,6'-dimethyl-2,2'-bipyridine (Me2bipy) or 2,9-dimethyl-1,10-phenanthroline (Me2phen) in THF at reflux temperature gives the trinuclear dihydride complexes [Ru3(mu-H)2(mu3-L1)(CO)8] (L1 = HCbipyMe 1 a, HCphenMe 1 b), which result from the activation of two C-H bonds of a methyl group. The hexa-, hepta-, and pentanuclear derivatives [Ru6(mu3-H)(mu5-L2)(mu-CO)3(CO)13] (L2 = CbipyMe 2 a, CphenMe 2 b), [Ru7(mu3-H)(mu5-L2)(mu-CO)2(CO)16] (L2 = CbipyMe 3 a, CphenMe 3 b), and [Ru5(mu-H)(mu5-C)(mu-L3)(CO)13] (L3 = bipyMe 4 a, phenMe 4 b) can also be obtained by treating 1 a and 1 b with [Ru3(CO)12]. Compounds 2 a and 2 b have a basal edge-bridged square-pyramidal metallic skeleton with a carbyne-type C atom capping the four Ru atoms of the pyramid base. The structures of 3 a and 3 b are similar to those of 2 a and 2 b, respectively, but an additional Ru atom now caps a triangular face of the square-pyramidal fragment of the metallic skeleton. The most interesting feature of 2 a, 2 b, 3 a, and 3 b is that their carbyne-type C atoms were originally bound to three hydrogen atoms in Me2bipy or Me2phen and, therefore, they arise from the unprecedented activation of all three C-H bonds of C-bound methyl groups. The pentanuclear compounds 4 a and 4 b contain a carbide ligand surrounded by five Ru atoms in a distorted trigonal-bipyramidal environment. They are the products of a series of processes that includes the activation of all bonds (three C-H and one C-C) of organic methyl groups, and are the first examples of complexes having carbide ligands that arise from C-bonded methyl groups. The alkenyl derivatives [Ru5(mu5-C)(mu-p-MeC6H4CHCHphenMe)(CO)13] (5 b), [Ru5(mu-H)(mu5-C)(mu-p-MeC6H4CHCHphenMe)(p-tolC2)(CO)12] (6 b), and [Ru5(mu-H)(mu5-C)(mu-PhCHCHphenMe)(PhC2)(CO)12] (7 b) have been obtained by treating 4 b with p-tolyl- and phenylacetylene, respectively. Their heterocyclic ligands contain an alkenyl fragment in the position that was originally occupied by a methyl group. Therefore, these complexes are the result of the formal substitution of an alkenyl group for a methyl group of 2,9-dimethyl-1,10- phenanthroline.

Journal Article↗
PubMed1998

Spectral and Electrochemical Behavior of Copper(II)-Phenanthrolines Bound to Calf Thymus DNA. [(5,6-dimethyl-OP)(2)Cu](2+) (5,6-dimethyl-OP = 5,6-Dimethyl-1,10-phenanthroline) Induces a Conformational Transition from B to Z DNA.

The interaction of 1:2 copper(II) complexes of 1,10-phenanthroline (OP) and variously methyl-substituted phenanthrolines with calf thymus DNA has been investigated by viscometry and spectral and electrochemical techniques. Viscometry and competitive ethidium bromide (EthBr) emission studies reveal that substitutions at 4- and 4,7-positions confer the complex a reduced affinity for DNA via partial intercalative interaction of the middle ring of OP between the base pairs of DNA, while substitutions at 5- and 5,6-positions confer a weak affinity toward DNA. The tetramethyl substitution at 3,4,7,8-positions lead to an intermediate behavior for the complex. Circular dichroism spectral studies of the interaction disclose for the first time that, of all the complexes, the 5,6-dimethyl-OP complex is a unique and remarkable reagent in that it reversibly binds to DNA and effects the important conversion of right-handed B DNA to left-handed Z DNA even in the presence of EthBr, an allosteric effector of the B conformation of DNA. This novel conformational transition is unexpected of the low GC content of natural DNA. The ratios of the binding constants (K(+)/K(2+)) for DNA binding of the Cu(I) and Cu(II) forms of the redox active OP complexes rather than the Cu(II)/Cu(I) redox potentials (0.023 to -0.098 V vs SCE) are good measures of the substituent dependent DNA cleavage efficiency and rate. They also reveal that the Cu(I) form of OP and 4-methyl- and 5,6-dimethyl-substituted OP complexes displays enhanced affinity to bind but noncovalently to the minor groove of DNA. Attempts have been made to illustrate the cleavage rate and efficiency of nucleolytic reactions in the light of the relative binding constants of Cu(I) and Cu(II) forms of the OP complexes.

Journal Article↗
PubMed1996

pi Molecular Orbital Crossing a(2)(chi)/b(1)(psi) in 1,10-Phenanthroline Derivatives. Ab Initio Calculations and EPR/ENDOR Studies of the 4,7-Diaza-1,10-phenanthroline Radical Anion and Its M(CO)(4) Complexes (M = Cr, Mo, W).

Ab initio, semiempirical, and HMO perturbation calculations were employed to assess the relative positioning of the closely situated low-lying unoccupied pi MOs a(2)(chi) and b(1)(psi) in 1,10-phenanthroline (phen) and its 3,4,7,8-tetramethyl (tmphen) and four symmetrical diaza derivatives (n,m-dap). Compared to a(2)(chi), the b(1)(psi) pi MO is distinguished by markedly higher MO coefficients at the chelating nitrogen pi centers in 1,10-positions; eventually, a higher Coulomb integral value at those positions will thus always favor the lowering of b(1) beyond a(2). Using the Coulomb integral parameter at the chelating 1,10-nitrogen pi centers as the HMO perturbation variable, the crossing of both energy levels in terms of decreasing preference for the a(2)(chi) over the b(1)(psi) orbital as the lowest unoccupied MO follows the sequence 5,6-dap > 2,9-dap > 4,7-dap > phen > 3,8-dap. The calculations reveal a(2)(chi) as the LUMO in 5,6-dap for all reasonable perturbation parameters, in agreement with previous observations for ruthenium(II) complexes which reveal a discrepancy between the lowest-lying "redox pi orbital" (a(2)) and the "optical pi MO" (b(1)) to which the most intense low-energy MLCT transition occurs. According to the HMO calculations, the situation is more ambiguous for the 4,7-dap analogue, yet EPR/ENDOR studies clearly show that the one-electron-reduced ligand and its tetracarbonylmetal(0) complexes (Cr, Mo, W) have the b(1)(psi) orbital singly occupied. Only ab initio calculations with double-zeta basis and inclusion of d polarization functions reproduced correctly the experimentally observed orbital ordering for tmphen (a(2) < b(1)) and for phen and 4,7-dap (b(1) < a(2)).

Journal Article↗
PubMed2000

cis-Bis(dicyanamido)bis(1,10-phenanthroline)manganese(II) and cis-bis(dicyanamido)bis(1,10-phenanthroline)zinc(II).

The title compounds are isomorphous, comprised of neutral monomeric [M(phen)(2)(dca)(2)] [(I): M = Mn, (II): M = Zn; phen is 1,10-phenanthroline, C(12)H(8)N(2); dca is dicyanamide, C(2)N(3)] molecules. In the molecule, the divalent metal ion is in a distorted octahedral coordination environment formed by six N atoms from the phen and dca ligands. The Mn-N [2.144 (2)-2.319 (2) A] and Zn-N [2.075 (2)-2.245 (2) A] distances are in agreement with the difference in size of the two divalent ions.

Journal Article↗
PubMed2003

Diaquabis(1,10-phenanthroline-kappa(2)N,N')manganese(II) thiodiglycolate bis(1,10-phenanthroline-kappa(2)N,N')(thiodiglycolato-kappa(2)O,O')manganese(II) tridecahydrate.

The title compound, [Mn(C(12)H(8)N(2))(2)(H(2)O)(2)](C(4)H(4)O(4)S).[Mn(C(4)H(4)O(4)S)(C(12)H(8)N(2))(2)].13H(2)O, contains one dianion of thiodiglycolic acid (tdga(2-)) and two independent manganese(II) moieties, viz. [Mn(phen)(2)(H(2)O)(2)](2+) and [Mn(tdga)(phen)(2)], where phen is 1,10-phenanthroline. The Mn(II) atoms are octahedrally coordinated by four N atoms of two bidentate phen ligands [Mn-N = 2.240 (2)-2.3222 (19) A] and either two water O atoms or two tdga carboxyl O atoms [Mn-O = 2.1214 (17)-2.1512 (17) A]. The tdga ligand chelates as an O,O'-bidentate ligand, forming an eight-membered ring with one Mn atom. The free tdga(2-) dianion is hydrogen bonded to an [Mn(phen)(2)(H(2)O)(2)](2+) ion, with O.O distances of 2.606 (2) and 2.649 (2) A. The crystal structure is further stabilized by an extensive network of hydrogen bonds involving 13 water molecules.

Journal Article↗
PubMed2004

(2,2'-Bipyridine-kappa2N,N')(1,1-cyclobutanedicarboxylato-kappa2O,O')palladium(II), (1,1-cyclobutanedicarboxylato-kappa2O,O')(1,10-phenanthroline-kappa2N,N')palladium(II) monohydrate and (1,1-cyclobutanedicarboxylato-kappa2O,O')(1,10-phenanthroline-kappa2N,N')palladium(II) dihydrate.

In the three title compounds, [Pd(C(6)H(6)O(4))(C(10)H(8)N(2))], (I), [Pd(C(6)H(6)O(4))(C(12)H(8)N(2))].H(2)O, (IIa), and [Pd(C(6)H(6)O(4))(C(12)H(8)N(2))].2H(2)O, (IIb), respectively, each Pd(II) atom has a similar distorted cis-planar four-coordination geometry, completed by two O atoms of a bidentate 1,1-cyclobutanedicarboxylate anion and two N atoms of either a 2,2'-bipyridine or a 1,10-phenanthroline ligand.

Journal Article↗
PubMed2006

A one-dimensional mixed-anion lead(II) coordination polymer: catena-poly[[(1,10-phenanthroline)lead(II)]-mu-benzoato-mu-nitrato-[(1,10-phenanthroline)lead(II)]-di-mu-benzoato].

In the title polymeric compound, [Pb2(C7H5O2)3(NO3)(C12H8N2)2]n, both independent Pb atoms adopt an eight-coordinate geometry formed by one nitrate, three benzoate and one 1,10-phenanthroline ligand. The one-dimensional polymer consists of dimeric [Pb2(C7H5O2)3(NO3)(C12H8N2)2] units, in which all nitrate and benzoate ligands act in a bridging-chelating coordination mode.

Journal Article↗
PubMed1999

[Photoluminescence and UV-VIS absorption spectra characteristics of complexes of ruthenium (II) with 1,10-phenanthroline and 4,7-diphnyl-1,10-phenanthroline].

The preparation and spectroscopic characteristics of the tris (1,10-phenanthroline) and tris (4,7-diphenyl-1,10-phenalthroline) complex ions of rathenium (II) are reported. Under the coordinate field with the property of D3 group, the splitting of the 4d state of Ru2+ is discussed. The transitions which give rise to the UV-VIS absorption spectra and emission spectra of the complexes are assigned. The influence of the coordinate substance on the absorptivity and red-shift is discussed as well.

English Abstract↗
PubMed1988

Structures of chloro(glycinato)(1,10-phenanthroline)copper(II) monohydrate (I) and aqua(1,10-phenanthroline)(L-phenylalaninato)copper(II) nitrate monohydrate (II).

(I) [CuCl(C2H4NO2)(C12H8N2)].H2O, Mr = 371.28, orthorhombic, P2(1)2(1)2(1), a = 6.795 (3), b = 12.496 (4), c = 17.273 (5) A, V = 1467 (1) A3, Dx = 1.680 Mg m-3, Z = 4, F(000) = 756, lambda(Mo K alpha) = 0.71069 A, mu(Mo K alpha) = 1.742mm-1. Room temperature. Final R = 0.046 for 1302 unique observed reflections. (II) [Cu(C9H10NO2)(C12H8N2)(H2O)]NO3.-H2O, Mr = 505.98, monoclinic, P2(1), a = 5.782 (2), b = 20.700 (6), c = 9.355 (3) A, beta = 97.58 (2)degrees, V = 1110 (1) A3, Dx = 1.514 Mg m-3, Z = 2, F(000) = 522, lambda(Mo K alpha) = 0.71069 A, mu(Mo K alpha) = 1.076 mm-1. Room temperature. Final R = 0.069 for 1929 unique observed reflections. The Cu ion displays distorted square-pyramidal coordination in both (I) and (II), with the chlorine atom (I) or the water molecule (II) in the apical position. The Cu-N bond lengths alter according to the electronegative character of the trans atom. The conformations of the five-membered chelate rings appear to depend on H bonding and van der Waals interactions.

Hydrogen Bonding↗
PubMed1997

Differential inhibition of the yeast bc1 complex by phenanthrolines and ferroin. Implications for structure and catalytic mechanism.

o-Phenanthroline and m-phenanthroline both inhibit the electron transfer activity of lauryl maltoside-solubilized yeast bc1 complex progressively with time. Pre-steady-state kinetics indicate that these compounds bind to the complex on the intermembrane space side, thereby blocking reduction of cytochrome b via the ubiquinol oxidation site. o-Phenanthroline is additionally capable of chelating an iron atom derived from the Rieske Fe-S cluster, thereby distorting the structure of the Rieske protein. EPR analysis shows that the secondary effect of o-phenanthroline occurs after initial inactivation and that m-phenanthroline, which lacks chelating activity, does not affect the Rieske Fe-S cluster. Spectral analysis shows that the b and c1 cytochromes are still dithionite-reducible after inactivation by o-phenanthroline, indicating that they remain intact. Inactivation by o-phenanthroline can be prevented by the addition of Fe2+. Surprisingly, ferroin, the o-phenanthroline-ferrous sulfate complex, also inhibits the bc1 complex activity. In contrast to o-phenanthroline, this effect is instantaneous. The two types of inhibition are clearly distinguishable by pre-steady-state reduction kinetics. Interestingly, ferroin can only inhibit electron transfer activity by about 50%. This behavior is discussed in relation to the dimeric structure of the bc1 complex, and we conclude that ferroin binds to only one of the two protomers. The rate of inactivation by o-phenanthroline is dependent on the incubation temperature and can be quantitated in terms of the half-life for a certain temperature, the time at which the bc1 activity is reduced to 50%. In contrast to the solubilized form, the bc1 complex in intact mitochondria is insensitive to o-phenanthroline, suggesting that the inactivation rate by o-phenanthroline is dependent on accessibility of the complex to the agent. Reaction with o-phenanthroline is thus a useful technique for study of structural stability of the bc1 complex under different conditions and should provide a sensitive tool for determination of the relative stability of mutant enzymes.

Chelating Agents↗
PubMed1981

The effects of 1,10-phenanthroline on the binding of activated rat hepatic glucocorticoid-receptor complexes to deoxyribonucleic acid-cellulose.

1,10-Phenanthroline, a metal ion chelator, inhibits the binding of previously activated (25 C for 30 min) rat hepatic [3H]triamcinolone acetonide (3H-labeled 9-fluoro-11 beta, 21-dihydroxy-16 alpha, 17-1-[1-metylethylidenebis(oxy)]pregna-1,4-diene-3,20-dione ([3H]TA)-receptor complexes to DNA-cellulose. The observed inhibition increases as the temperature of the preincubation with chelator is increased from 0 to 25 C. Fifty percent of the maximal inhibition (greater than 90%) detected at 25 C is achieved with 1 mM 1,10-phenanthroline. The observed inhibition is not the consequence of DNA degradation by 1,10-phenanthroline-Cu2+ complexes, since preincubation of activated cytosol with neocuproine (2,9-dimethyl-1,10-phenanthroline), a potent Cu2+ chelator, fails to block the subsequent inhibition of DNA-cellulose binding by 1,10-phenanthroline. The failure of other chelators which complex siilar metal ions (alpha, alpha'-dipyridyl,8-hydroxyquinoline, 2,2',2"-tripyridine, EDTA, EGTA, and Na azide) to inhibit DNA-cellulose binding suggests that the effectiveness of 1,10-phenanthroline does not result from removal of a required free metal ion(s) but, rather, from a specific interaction with a metal ion(s) which may be located within the activated receptor protein. The observed inhibition is dependent on the metal chelating properties of 1,10-phenanthroline, since preincubation with several divalent metal cations (Zn2+, Co2+, and Ni2+) which are known to be chelated by this compound block its subsequent inhibitory effect. Ferroin (1,10-phenanthroline-ferrous sulfate complex) and 1,7-phenanthroline (nonchelating isomer) also fail to inhibit DNA-cellulose binding. The inhibition mediated by 1,10-phenanthroline persists after gel filtration, suggesting that 1,10-phenanthroline associated with a macromolecule is the effective form of the inhibitor, rather than free 1,10-phenanthroline. Finally, 1,10-phenanthroline appears to interact directly with activated [3H]TA-receptor complexes, since it alters their net charge and results in their elution from DEAE-cellulose at a salt concentration characteristic of unactivated complexes. Collectively, the data suggest that the activated [3H]TA-receptor complex is a metalloprotein and that the metal ion(s) may be associated directly with the DNA-binding site or may regulate this site indirectly through an allostreic mechanism.

Adrenalectomy↗