Dilatometric constant for polymerization of α-methylstyrene

By measurement of the specific volume of solutions of poly-α-methylstyrene in α-methylstyrene monomer at 25°C, the dilatometric constant was found to be K_D = (0.002007 ± 0.000030)%^?1. Estimation of the temperature dependence resulted in the equation (K_D)_t = 1.81 × 10^?3 + 7.82 + 10^?6 t, where t denotes temperature in °C.     

Ion-aggregation and thermal expansion in styrene-based ionomers

The linear thermal-expansion coefficients (α) of styrene–sodium methacrylate copolymers were studied as a function of the concentration of sodium methacrylate comonomer. Over the concentration range studied (0.61–9.0 mole % sodium methacrylate), the expansion coefficients of the glass α_g and of the liquid α_l were independent of ion concentration. Average values for these quantities were α_g = (6.9 ± 0.9) × 10^?5 deg^?1 and α_l = (16.0 ± 2.0) × 10^?5 deg^?1. When samples of concentrations above 6 mole % were heated from room temperature, a low value for the liquid-expansion coefficient α_l was observed in the first runs. This quantity had an average value of (12.0 ± 1.9) × 10^?5 deg^?1. Heating of the 6.5 mole % sample from room temperature followed by cycling from the glass transition temperature T_g to successively higher temperatures resulted in a gradual increase in liquid-expansion coefficient. The results are consistent with the hypothesis of the existence of various types of ionic aggregates in these polymers, with the state of aggregation changing at approximately (5–6) % of ions. Experimental T_g values, which increase with ion concentration over the entire range, are consistent with the results of previous studies.     

Preparation,fractionation, and dilute-solution behavior of ABA poly(methyl methacrylate-b-α-methylstyrene) block copolymers

The preparation by anionic polymerization of six ABA poly(methyl methacrylate-b-α-methylstyrene) block copolymers and of sixteen poly(α-methylstyrene)s is described. The block copolymers, of similar molecular weight but with different chemical compositions, were fractionated by preparative gel permeation chromatography and their behavior in dilute solution was investigated using viscometry. The results obtained indicate that the intramolecular phase separation does not occur under the conditions utilized, the block copolymers assuming randomcoil configurations in all of the copolymer/solvent systems studied. Consequently the block copolymer molecules are more expanded than homopolymers of the same molecular weight. The series of poly(α-methylstyrene)s covered the molecular weight range 2.7 × 10³–1.3 × 10⁶ and enabled the determination of Mark–Houwink–Sakurada constants for poly(α-methylstyrene) in the solvents chosen for the block copolymer studies.     

Low-frequency dynamic mechanical behavior of lightly crosslinked 1,5-trans-polypentenamer in the rubberlike region

The low-frequency (10^?3 to 5 × 10^?1 Hz) dynamic mechanical properties were obtained over the temperature range of 25 to 96°C for 1,5-trans-polypentenamer networks prepared in the presence of 0,0.01, 0.02, 0.04, 0.1, 0.2, and 0.4% dicumyl peroxide. For comparison, similar properties of 1,4-polybutadiene crosslinked with 0.02% dicumyl peroxide were also measured. Superimposed curves for the components of the dynamic compliance, J_p′ and J_p″, reduced to 25°C were obtained and the retardation spectra L were calculated over a range of four logarithmic decades deep in the rubberlike region. It was found that networks containing 0.04 and 0.1% DCP have a small loss maximum J_p″ in the reduced frequency region log ωa_T between ?2 and 0 which can be assigned to relaxations of untrapped entanglements. The values of (J_p′ ? 1/ωη) for very lightly crosslinked polypentenamer networks approached equilibrium very slowly compared to 1,4-polybutadiene crosslinked to the same degree, which suggests the participation of very long retardation times of this polymer which is also probably reflected in the comparatively high values of C₂ of the Mooney–Rivlin equation.     

Viscoelastic properties of 1,2-polybutadiene—comparison with natural rubber and other elastomers

Viscoelastic properties of uncrosslinked 1,2-polybutadiene (91.5% vinyl, 7.0% cis, 1.5% trans, number-average molecular weight 99,000) were studied by dynamic shear measurements between 0.15 and 600 cps (torsion pendulum and Fitzgerald transducer) and shear creep measurements over time periods up to 3.7 × 10⁴ sec., in the temperature rang from 5 to 50°C. More limited dynamic measurements were made on a sample of unvulcanized natural rubber with number-average molecular weight 350,000 at frequencies from 0.4 to 400 cps and temperatures from 13 to 48°C. All data were reduced to 25°C. by shift factors calculated from equations of the WLF form with the following coefficients: 1,2-polybutadiene, c₁ = 6.23, c₂ = 72.5; natural rubber, c₁ = 5.94, c₂ = 151.6. In the transition zone, the relative positions of the loss tangent curves on the logarithmic frequency scale for these and other rubbers (1,4-polybutadiene with 50% trans configuration; styrene–butadiene rubber with 23.5% styrene content; and polyisobutylene) provided relative measures of local segment mobility. At 25°C., these ranged over a factor of 3700 with 1,2-polybutadiene and polyisobutylene the lowest and 1,4-polybutadiene the highest. When the frequency scale of each rubber was reduced to a temperature 100°C. above its glass transition temperature, however, the loss tangent curves for all except polyisobutylene were nearly coincident; the latter still showed a lower mobility by a factor of about 1/800. The terminal relaxation time and steady-state compliance for the 1,2-polybutadiene calculated from the Rouse theory were larger than those observed experimentally. The level of compliance corresponding to the entanglement network of 1,2-polybutadiene, J_eN, was calculated by integration over the loss compliance, J″, to be 1.62 × 10^?7 cm.²/dyne; integration over G″ to obtain the corresponding modulus gave reasonable agreement. From such J_eN, values, the average number of chain atoms between entanglement points, jZ_e, was estimated as follows: 1,2-polybutadiene, 132; natural rubber, 360; 1,4-polybutadiene, 110; styrene–butadiene rubber, 186; polyisobutylene, 320. Values of jZ_e were also estimated from the minimum in the loss tangent and compared with those reported from the molecular weight dependence of viscosity. The three sources were in generally good agreement.     

Trityl salt—initiated polymerization of α-methylstyrene

The initiation reaction of the polymerization of α-methylstyrene by trityl tetrachloroferate and tritylhexachloroantimonate in 1,2-dichloroethane at 20°C was studied. The rate constants were 14 × 10^?3 and 27 × 10^?3 L mol^?1s^?1, respectively. The dissociation constants of tritylterachloroferate (K_d = 0.88 × 10^?4M^?1) and tritylhexachloroantimonate (K_d = 2.64 × 10^?4M^?1) was determined. The effect of electron acceptors and donors on the dissociation equilibrium and initiation rate was investigated. It was shown that in strongly dissociated ion pairs such as stable carbenium salts the electron donors and acceptors have no appreciable effect on the magnitude of the dissociation. The temperature dependence of the rate constants in the ?20–+20°C range yielded the following thermodynamic parameters for trityltetrachloroferate: E_i = 8.54 kcal/mol; A = 3.2 × 10⁴ mol^?1s^?1; ΔH* = 8 kcal/mol; and S* = ?39.8 eu.     

Encapsulation‐Induced Remarkable Stability of a Hydrogen‐Bonded Heterocapsule

Remarkably enhanced stability of the self‐assembled hydrogen‐bonded heterocapsule 1?2 by the encapsulation of 1,4‐bis(1‐propynyl)benzene 3 a was found with K_a=1.14×10⁹ M ^?1 in CDCl₃ and K_a2=1.59×10⁸ M ^?2 in CD₃OD/CDCl₃ (10 % v/v) at 298 K. The formation of 3 a @( 1?2 ) was enthalpically driven (ΔH°<0 and ΔS°<0) and there was a unique inflection point in the correlation between ΔH° versus ΔS° as a function of polar solvent content. The ab initio calculations revealed that favorable guest–capsule dispersion and electrostatic interactions between the acetylenic parts (triple bonds) of 3 a and the aromatic inner space of 1?2 , as well as less structural deformation of 1?2 upon encapsulation of 3 a , play important roles in the remarkable stability of 3 a @( 1?2 ).     

ULTRASONIC RELAXATION KINETICS OF PLANAR:OCTAHEDRAL EQUILIBRIA OF A NICKEL MACROCYCLIC COMPLEX

Abstract

The equilibrium between the diamagnetic, planar nickel(II) macrocyclic complex known as NiCR²⁺(CR is 2,12-dimethyl-3,7,11,17-tetraazabicyclo[11.3.1]heptadeca-1(17),2, 11,13,15pentaene) and its paramagnetic, six-coordinate dimethanol adduct has been examined in methanol solution as the tetrafluoroborate salt. From the temperature dependence of the electronic absorption spectrum, thermodynamic parameters of ΔH°₄₆ = ?4.35 kcal mol^?1 and ΔS°₄₆ = ?8.72 cal deg^?1 mol^?1 were determined. From the excess ultrasonic absorption a relaxation frequency of 15 MHz was observed from which rate constants of k₄₆ of 8.6 × 10⁷ s^?1 and k₆₄ of 7.9 × 10⁶ s^?1 were calculated. The rate constant k₄₆ is nearly the same as the rate constant for solvent exchange which had previously been determined by NMR. This implies that the solvent exchange is effected by the octahedral-planar equilibrium and that a two-step mechanism with a five-coordinate intermediate can be eliminated.     

Molecular weight distribution studies. I. Radiation-induced polymerization of liquid α-methylstyrene

The concentration of water in purified and BaO-dried α-methylstyrene was found to be 1.1 × 10^?4M. The radiation-induced bulk polymerization of the α-methylstyrene thus prepared was studied in the temperature range of ?20°C to 35°C. The polymerization rate varied as the 0.55 power of the dose rate. The theoretical molecular weights and molecular weight distribution were calculated from a proposed kinetic scheme and these values were then compared with those found experimentally. The agreement between these two was reasonably close, and therefore it was concluded that, from the molecular weight distribution point of view, the proposed kinetic scheme for the cationic polymerization of α-methylstyrene is an acceptable one. The rate constant for chain transfer to monomer k_f changed with temperature and was found to be responsible for the decrease in the molecular weight of the polymer with increase in temperature. k_f and k_p at 20°C were found to be 0.95 × 10⁴ l./mole-sec and 0.99 × 10⁶ l./mole-sec, respectively.     

Temperature dependence of unperturbed dimensions for isotactic poly(2-hydroxyethyl methacrylate)

The unperturbed dimensions of isotactic poly(2-hydroxyethyl methacrylate) (PHEMA) were evaluated from intrinsic viscosity measurements in water, ethanol, 1-propanol, 2-propanol, and 2-butanol under θ conditions over the temperature range of 3.7–32.1°C. The smallest value of unperturbed dimensions (K_θ) and the largest negative temperature dependence of unperturbed dimensions and the polymer–solvent interaction parameter (B) were obtained in aqueous θ solvent relative to the corresponding organic θ solvents. These results were interpreted by the hydrophobic interaction between the hydrophobic groups of isotactic PHEMA and water solvent. The temperature coefficient of the unperturbed dimensions, d ln〈r〉/dT, obtained in this study has a negative value of ?1.44 × 10^?3 deg^?1 under chemically similar θ solvents such as ethanol, 1-propanol, 2-propanol, and 2-butanol where specific solvent effects are eliminated or minimized. In order to obtain the thermodynamic parameters for mixing between isotactic PHEMA and solvents, the plots of the polymer–solvent interaction parameter versus reciprocal absolute temperature (1/T) were carried out. Both the entropy of dilution and enthalpy of dilution show the negative values for water, methanol, and t-butanol, whereas the positive ones for ethanol, 1-propanol, 2-propanol, and 2-butanol. This result indicates that the solution of isotactic PHEMA behave as exothermal systems in the former class of solvents and endothermal ones in the latter class of solvents.     

Polymerization of acrylamide with persulfate–thiomalic acid initiator

The redox system of potassium persulfate–thiomalic acid (I₁–I₂) was used to initiate the polymerization of acrylamide (M) in aqueous medium. For 20–30% conversion the rate equation is where R_p is the rate of polymerization. Activation energy is 8.34 kcal deg^?1 mole^?1 in the investigated range of temperature 25–45°C. M_n is directly proportional to [M] and inversely to [I₁]. The range of concentrations for which these observations hold at 35°C and pH 4.2 are [I₁] = (1.0–3.0) × 10^?3, [I₂] = (3.0–7.5) × 10^?3, and [M] = 5.0 × 10^?2–3.0 × 10^?1 mole/liter.     

Use of samarium (III) acetate as initiator in ring-opening polymerization of trimethylene carbonate

Abstract

In this work was evaluated the activity of samarium acetate (III) (Sm(OAc)₃) as a possible initiator in the polymerization by ring opening of trimethylene carbonate (TMC). All polymerizations were carried out under solvent-free melt conditions in ampoules-like flasks, equipped with a magnetic stirrer. The effects of different parameters of reaction, such as molar ratio monomer to initiator, temperature and reaction time, on typical variables of polymers, e.g., conversion of TMC to poly(trimethylene carbonate) (PTMC), dispersity and molar mass, were analyzed. The molar ratio of monomer to initiator was varied between 0 and 1000?mol/mol and the temperature among 70 and 150?°C. Nuclear Magnetic Resonance (¹H-NMR and HMBC) and Size Exclusion Chromatography (SEC) were used to characterize the polymers. The results indicate that the Sm(OAc)₃ induces the polymerization of TMC to high conversion with number-average molecular weights of 3.11?×?10³ to 38.40?×?10³?Da. Based on the ¹H-NMR end-group analysis of low-molecular-weight PTMC, it was proposed a coordination–insertion mechanism for the polymerization, with a breakdown of the acyl-oxygen bond of the TMC. In according to the kinetic study carried out, the polymerization rate is first-order with respect to monomer concentration with apparent rate constants of k_ap?=?7.02?×?10^?4?mol?×?L^?1?×?h^?1.     

Piezoelectricity in oriented films of poly(γ-benzyl-L-glutamate)

Oriented films of poly(γ-benzyl L -glutamate) (PBLG) were prepared by two methods. Films of PBLG cast from chloroform solutions were elongated by rolling at 70°C. A solution of PBLG in methylene bromide was placed in a magnetic field of about 7000 gauss and the solvent was slowly evaporated for a few days until an oriented film was obtained. The real and imaginary components of the complex piezoelectric strainconstant d₂₅^* = d₂₅′ ? jd₂₅″ were determined over the temperature range from ?180°C to +180°C at a frequency of 20 Hz. The constants showed dispersions at about 20°C and about 100°C, where dynamic viscoelastic dispersions were also observed. Degree of crystallinity X_c and degree of orientation II_a of crystallites were determined from x-ray diffraction diagrams. The product X_cII_α and the value of d₂₅′ at room temperature were found to be linearly related, and both showed a maximum at an elongation ratio of 1.5 (the ratio of the final to initial length) for roll-oriented films and at an initial solution concentration of 15% by weight for magnetically oriented films. The largest values of d₂₅′ were approximately 2 × 10^?12 and 4 × 10^?12 coulomb/newton, respectively, at room temperature.     

Temperature dependence of limiting viscosity number and radius of gyration of cellulose diacetate in acetone

Acetone solutions of a cellulose diacetate fraction were studied by viscosity and light scattering methods over the range 12.6–50.3². The temperature dependences of the limiting viscosity number [η], the mean-square radius of gyration 〈s²〉, and the second virial coefficient A₂ were determined. The unperturbed mean-square radius of gyration 〈s²〉_o and the expansion factor α, were estimated by using theoretical relations to the interpenetration function. It was found that dln 〈s²〉_o/dT is ?6.4 × 10^?3 deg^?1, while α, is close to unity over the whole temperature range studied. The viscosity results are interpreted to show that the draining effect is not negligible and the Flory viscosity parameter Φ slightly increases with increasing temperature. It is finally concluded that the value of ?6.9 × 10^?3 deg^?1 for dln [η]/dT can be ascribable to the rapid decrease in 〈s²〉_o.     

On the kinetics of polymer degradation in solution—VII. Laser flash photolysis of poly-α-methylstyrene in solution

Poly-α-methylstyrene (PαMS) was degraded in CHCl₃ and CCl₄ solution by flash photolysis (λ = 265 nm). The degradation, as detected by light scattering measurements, is caused by the attack on PαMS by solvent radicals, assumed to be formed mainly by energy transfer processes. The direct effect did not lead to detectable main chain cleavage as evidenced by experiments with PαMS dissolved in dioxane or methylene chloride. The time dependence of the decrease of the light scattering intensity (LSI) after the flash was measured. The observed first order lifetime τ(LSI) corresponds to the lifetime of lateral macroradicals P′ that decompose by main chain cleavage (k = 3.5 × 10² sec^?1). Molecular oxygen reacts with the lateral macroradicals with k = (5.5 ± 0.5) 10⁵ M^?1 sec^?1. Only a minor portion of the product of this reaction (PO₂′) decays by main chain scission. Thus O₂ inhibits main chain scission significantly. By addition of cyclohexane and ethyl mercaptan, the main chain cleavage is inhibited. τ(LSI) was not affected by these compounds in the concentration range investigated ([C₆H₁₂]: up to 8.4 M; [C₂H₅SH]: up to 3 × 10^?3 M), indicating that they reacted with solvent radicals which otherwise attack the polymer forming lateral macroradicals.     

Synthesis,properties, and field effect transistor characteristics of new thiophene‐[1,2,5]thiadiazolo[3,4‐g]quinoxaline‐thiophene‐based conjugated polymers

Four new conjugated copolymers based on the moiety of bis(4‐hexylthiophen‐2‐yl)‐6,7‐diheptyl‐[1,2,5]thiadiazolo[3,4‐g]quinoxaline (BTHTQ) were synthesized and characterized, including poly(6,7‐diheptyl‐4,9‐bis(4‐hexylthiophen‐2‐yl)‐[1,2,5]thiadiazolo[3,4‐g]quinoxaline) (PBTHTQ), poly‐(6,7‐diheptyl‐4,9‐bis(4‐hexylthiophen‐2‐yl)‐[1,2,5]thiadiazolo‐[3,4‐g]quinoxaline‐alt‐2,5‐thiophene) (PTTHTQ), poly(6,7‐diheptyl‐4,9‐bis(4‐hexylthiophen‐2‐yl) [1,2,5]‐thiadiazolo‐[3,4‐g]quinoxaline‐alt‐9,9‐dioctyl‐2,7‐fluore‐ne) (PFBTHTQ), and poly(6,7‐diheptyl‐4,9‐bis(4‐hexylthiophen‐2‐yl)‐[1,2,5]thiadiazolo[3,4‐g]quinoxaline‐alt‐1,4‐bis(decyloxy)phenylene) (PPBTHTQ). The λ_max of PBTHTQ, PTTHTQ, PFBTHTQ, and PPBTHTP thin films was shown at 780, 876, 734, and 710 nm, respectively, with the corresponding optical band gaps (E) of 1.31, 1.05, 1.40, and 1.43 eV. The relatively small band gaps of the synthesized polymers suggested the significance of intramolecular charge transfer between the donor and TQ moiety. The estimated hole mobilities of PBTHTQ, PTTHTQ, and PFBTHTQ‐based field effect transistor devices using CHCl₃ solvent were 8.5 × 10^?5, 8.5 × 10^?4, and 2.8 × 10^?5 cm² V^?1 s^?1, respectively, but significantly enhanced to 1.6 × 10^?4, 3.8 × 10^?3, and 1.5 × 10^?4 cm² V^?1 s^?1 using high boiling point solvent of chlorobenzene (CB). The higher hole mobility of PTTHTQ than the other two copolymers was attributed from its smaller band gap or ordered morphology [wormlike (chloroform) or needle‐like (CB)]. The characteristics of small band gap and high mobility suggest the potential applications of the BTHTQ‐based conjugated copolymers in electronic and optoelectronic devices. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 6305–6316, 2008     

Kinetic Studies of the Ligand Substitution Reaction of Some New Uranyl Schiff Base Complexes with Tri‐n‐butylphosphine

Kinetics of the substitution reaction of solvent molecule in uranyl(VI) Schiff base complexes by tri‐n‐butylposphine as the entering nucleophile in acetonitrile at 10–40°C was studied spectrophotometrically. The second‐order rate constants for the substitution reaction of the solvent molecule were found to be (8.8 ± 0.5) × 10^?3, (5.3 ± 0.2) × 10^?3, (7.5 ± 0.3) × 10^?3, (6.1 ± 0.3) × 10^?3, (13.5 ± 1.6) × 10^?3, (13.2 ± 0.9) × 10^?3, (52.9 ± 0.2) × 10^?3, and (88.1 ± 0.6) × 10^?3 M^?1 s^?1 at 40°C for [UO₂(Schiff base)(CH₃CN)], where Schiff base = L1–L8, respectively. In a temperature dependence study, the activation parameters ΔH^# and ΔS^# for the reaction of uranyl complexes with PBu₃ were determined. From the linear rate dependence on the concentration of PBu₃, the span of k₂ values and the large negative values of the activation entropy, an associative (A) mechanism is deduced for the solvent substitution. By comparing the second‐order rate constants k_2, it was concluded that the steric and the electronic properties of the complexes were important for the rate of the reactions.     

Hydrodynamic invariant of polymer molecules

The theories of hydrodynamic properties of macromolecules in solution leading to an invariant relationship between the values of the intrinsic viscosity, [η], the molecular weight, M, and the translational friction coefficient of the molecule, f, have been considered. The review of experimental data comprising as much as about 2000 fractions of various polymers suggests that for all flexible-chain and moderately rigid-chain molecules the hydrodynamic parameter A₀ = kη₀(M[η]/100)^1/3f^?1 is actually an invariant independent of the chain length and the thermodynamic strength of the solvent and for moderately polydisperse samples also independent of the degree of their polydispersity. For polymers with very rigid chains the parameter A₀ has a high value over the experimentally investigated range of M. These conclusions make it possible to recommend the use of the following average experimental values of the invariant A₀ for the determination of M of polymers from the values of [η] and f: for flexible-chain and synthetic polymers with moderately high chain rigidity (3.2 ± 0.2) · 10^?10, for polymers with high chain rigidity (3.7 ± 0.4) · 10^?10, and for cellulose derivatives and other polysaccharides with molecular dispersity of nonelectrolyte solutions (3.30 ± 0.30) · 10^?10 erg deg^?1 mol^?1/3. The fact that the experimental value of A₀ = 3.2 · 10^?10 does not coincide with the value of A_∞ = 3.8 · 10^?10 erg deg^?1 mol^?1/3 predicted by the theories of translational friction and viscosity of macromolecules implies that the theoretical values of P_∞ = 5.11 and Φ_∞ = 2.8 · 10²³ mol^?1 are mutually incompatible and these theories require further development.     

Configurational characteristics of trans-1,4-polychloroprene: Experimental results on the unperturbed dimensions and their temperature coefficient

Polychloroprene [CCl?CH? CH₂? CH₂? ]_x of approximately 95% trans-1,4 stereochemical structure was prepared by low-temperature emulsion polymerization. Fractions, obtained by liquid–liquid precipitations were studied in toluene solutions at 30°C by viscometry and osmometry. In addition, force–temperature measurements were carried out on networks of the polymer in the amorphous state. The results obtained on the polymer solutions indicate that the unperturbed dimensions of trans-1,4-polychloroprene are essentially the same as those of trans-1,4-polybutadiene of the same molecular weight. This observation, that substitution of a relatively large Cl atom for one of the methine H atoms in the trans-1,4-polybutadiene repeat unit has little effect on the chain dimensions, suggests that this increase in substituent size is offset by the fact that the length of a C? Cl bond is very much greater than that of a C? H bond. The results obtained on the polymer networks indicate that the unperturbed dimensions of trans-1,4-polychloroprene decrease significantly with increasing temperature, as has also been reported for both trans-1,4-polybutadiene and trans-1,4-polyisoprene.     

Nuclease activity of redox/non-redox active binuclear transition metal mixed-polypyridine complexes: [M2(1,4-tpbd)(diimine)2(H2O)2]4+, M = Zn,Co, Ni,Cd, diimine = phen,bpy, dafo

Seven new transition metal complexes formulated as [M₂(1,4-tpbd)(diimine)₂(H₂O)₂]⁴⁺ [M = Zn, Co, Ni, Cd; 1,4-tpbd = N,N,N′,N′-tetrakis(2-pyridylmethyl)benzene-1,4-diamine; diimine is a N,N-donor heterocyclic base like 1,10-phenanthroline (phen), 2,2′-bipyridine (bpy), 4,5-diazafluoren-9-one (dafo)] have been synthesized and structurally characterized by X-ray crystallography: [Zn₂(1,4-tpbd)(phen)₂(H₂O)₂]⁴⁺ (1), [Zn₂(1,4-tpbd)(bpy)₂(H₂O)₂]⁴⁺ (2), [Co₂(1,4-tpbd)(phen)₂(H₂O)₂]⁴⁺ (3), [Ni₂(1,4-tpbd)(phen)₂(H₂O)₂]⁴⁺ (4), [Ni₂(1,4-tpbd)(bpy)₂(H₂O)₂]⁴⁺ (5), [Ni₂(1,4-tpbd)(dafo)₂(H₂O)₂]⁴⁺ (6) and [Cd₂(1,4-tpbd)(phen)₂(H₂O)₂]⁴⁺ (7). Single crystal diffraction reveals that the metals in the complexes are all in a distorted octahedral geometry. The interactions of the seven complexes with calf thymus DNA (CT-DNA) have been investigated by UV absorption, fluorescence, circular dichroism spectroscopy and viscosity measurements. The apparent binding constants (K_app) are calculated to be 5.2?×?10⁵ M^?1 for 1, 1.05?×?10⁵ M^?1 for 2, 5.76?×?10⁵ M^?1 for 3, 4.57?×?10⁵ M^?1 for 4, 1.29?×?10⁵ M^?1 for 5, 1.7?×?10⁵ M^?1 for 6, 2.53?×?10⁵ M^?1 for 7, the binding propensity to the calf thymus DNA in the order: 3 (Co-phen) > 1 (Zn-phen) > 4 (Ni-phen) > 7 (Cd-phen) > 6 (Ni-dafo) > 5 (Ni-bpy) > 2 (Zn-bpy). Furthermore, these complexes display efficient oxidative cleavage of supercoiled DNA; the Zn(II)/H₂O₂ and Cd(II)/H₂O₂ systems efficiently cleave DNA attributed to the peroxide ion coordinated to the Zn(II) and Cd(II), which enhanced their nucleophilicity, this is rare.