Single-crystal EPR Spectroscopy Research Articles

A Stable Aluminum Tris(dithiolene) Triradical.

A stable aluminum tris(dithiolene) triradical (3) was experimentally realized through a low-temperature reaction of the sterically demanding lithium dithiolene radical (2) with aluminum iodide. Compound 3 was characterized by single-crystal X-ray diffraction, UV-vis and EPR spectroscopy, SQUID magnetometry, and theoretical computations. The quartet ground state of triradical 3 has been unambiguously confirmed by variable-temperature continuous wave EPR experiments and SQUID magnetometry. Both SQUID magnetometry and broken-symmetry DFT computations reveal a small doublet-quartet energy gap [ΔEDQ = 0.18 kcal mol-1 (SQUID); ΔEDQ = 0.14 kcal mol-1 (DFT)]. The pulsed EPR experiment (electron spin echo envelop modulation) provides further evidence for the interaction of these dithiolene-based radicals with the central aluminum nucleus of 3.

Coligands Controlled Reactivities of Ruthenium(II) Precursors: Antiferromagnetically Coupled Ruthenium(III)-Phenoxyl versus Ruthenium(II)-Phenoxyl Forms.

The study disclosed that the reactivities of [RuII (PPh3)3Cl2] and [RuII(PPh3)3(CO)(H)Cl] precursors toward a trimethoxyarylimino-phenol derivative are sensibly different. The former promotes methoxy demethylation reaction affording a [Phenolato-RuIII-Phenolato] unit, while the latter containing π-acidic CO and hydride as coligands leads to C-H activation reaction, generating a [Phenolato-RuII-Aryl] unit. Notably, the oxidized analogues of these two forms produce antiferromagnetically coupled [RuIII-phenoxyl] and paramagnetic [RuII-phenoxyl] forms, which exhibit diverse reactivities. Surprisingly, the magnetically coupled [RuIII-phenoxyl] form obtained from [Phenolato-RuIII-Phenolato] motif leads to coligand, PPh3 oxidation and undergoes dimerization, making a Ru-Ru bond (2.599(2) Å), while the [RuII-phenoxyl] form obtained from [Phenolato-RuII-Aryl] motif leads to C-C coupling and H abstraction reactions. The coupling reaction affords a 4,4'-dibenzosemiquinonate anion radical complex, but the H-abstraction of the phenoxyl form gives a [RuII-Phenol] complex. For comparison, [RuII(IQR0)] and [RuII(ISQR·-)] complexes were also isolated, where IQR0 and ISQR·- are p-R-o-iminobenzoquinone and p-R-o-iminobenzosemiquinonate anion radicals. However, they fail to promote any bond-formation reaction. The molecular and electronic structures of the ruthenium (II/III) complexes were confirmed by single-crystal X-ray crystallography, EPR spectroscopy, and DFT calculations.

Nickel(I)-Phenolate Complexes: The Key to Well-Defined Ni(I) Species.

Phosphine-stabilized monovalent nickel complexes play an important role in catalysis, either as catalytically active species or as decomposition products. Most routes to access these complexes are highly ligand specific or rely on strong reducing agents. Our group recently disclosed a path to access nickel(I)-phenolate complexes from bis(1,5-cyclooctadiene)nickel(0) (Ni(cod)2). Herein, we demonstrate this protocol's broad applicability by ligating a wide range of mono- and bidentate phosphine ligands. We further show the versatility of the phenolate fragment as a precursor to nickel(I)-alkyl or aryl species, which are relevant to Ni catalysis or synthetically useful nickel(I)-chloride and hydride complexes. We also demonstrate that the chloride complex can be synthesized in a one-pot procedure starting from Ni(cod)2 in good yield, making this protocol a valuable alternative to current procedures. Single-crystal X-ray diffraction, IR, and EPR (or NMR) spectroscopy were employed to characterize all of the synthesized nickel complexes.

A Triply Negatively Charged Nanographene Bilayer with Spin Frustration.

There is resurgent interest in atomically precise nanographene radical ions composed of fused hexagons. Two monoradical anions can readily form a doubly negatively charged π-dimer, but to our knowledge, no triply negatively charged π-dimer species have been isolated till now. Herein we report the largest open-shell grapheneic bilayer and also the first example of triply negatively charged radical π-dimer. Upon three-electron reduction, bilayer nanographene fragment molecule (C96H24Ar6)2 (Ar = 2,6-dimethylphenyl) (12) was transformed to a triply negatively charged species 123•-, which has been characterized by single-crystal X-ray diffraction, EPR spectroscopy and SQUID measurements. 123•- features a 96-center-3-electron (96c/3e) pancake bond with a doublet ground state, which can be thermally excited to a quartet state. It is the largest open-shell nanographene bilayer species till now constructed with 34 π-fused rings with 96 conjugated sp2 carbon atoms. Spin frustration is observed with the frustration parameter f = |θcw|/TN > 31.8 at low temperatures in 123•-, which indicates graphene upon reduction doping may behave as quantum spin liquids.

Synthesis and Chemical Redox Studies of Half-Sandwich Chromium Carbonyl Azobenzenes

Chemical oxidation of piano-stool complexes Cr(CO)3(TripN═NTrip) (1) and Cr(CO)3(TripN═NTrip)Cr(CO)3 (2) was investigated, which led to a CAArN cation (cyc-1+) and a 17-electron chromic radical cation (2•+) upon one-electron oxidation reactions, respectively. The reactivity of cation cyc-1+ was extensively investigated. The electrophilicity enables cyc-1+ to form Lewis adducts with Me3P. Cyc-1+ can be reduced by metal K to form neutral monoradical cyc-1• and react with p-benzoquinone to produce a diradical dication salt (X). The electronic properties of 2•+ were investigated by single-crystal X-ray diffraction and EPR spectroscopy, in conjunction with DFT calculations.

Umpolung in a Pair of Cobalt(III) Terminal Imido/Imidyl Complexes.

Reaction of the CoI complex [(TIMMNmes)CoI](PF6) (1) (TIMMNmes= tris‐[2‐(3‐mesityl‐imidazolin‐2‐ylidene)‐methyl]amine) with mesityl azide yields the CoIII imide [(TIMMNmes)CoIII(NMes)](PF6) (2). Oxidation of 2 with [FeCp2](PF6) provides access to a rare CoIII imidyl [(TIMMNmes)Co(NMes)](PF6)2 (3). Single‐crystal X‐ray diffractometry and EPR spectroscopy confirm the molecular structure of 3 and its S=1/2 ground state. ENDOR, X‐ray absorption spectroscopy and computational analyses indicate a ligand‐based oxidation; thus, an imidyl‐radical electronic structure for 3. Migratory insertion of one ancillary NHC to the imido ligand in 2 gives the CoI N‐heterocyclic imine (4) within 12 h. Conversely, it takes merely 0.5 h for 3 to transform to the CoII congener (5). The migratory insertion in 2 occurs via a nucleophilic attack of the imido ligand at the NHC to give 4, whereas in 3, a nucleophilic attack of the NHC at the electrophilic imidyl ligand yields 5. The reactivity shunt upon oxidation of 2 to 3 confirms an umpolung of the imido ligand.

Comparing the Electronic Structure of Iron, Cobalt, and Nickel Compounds That Feature a Phosphine-Substituted Bis(imino)pyridine Chelate

It was recently discovered that (Ph2PPrPDI)Mn (PDI = pyridine diimine) exists as a superposition of low-spin Mn(II) that is supported by a PDI dianion and intermediate-spin Mn(II) that is antiferromagnetically coupled to a triplet PDI dianion, a finding that encouraged the synthesis and electronic structure evaluation of late first row metal variants that feature the same chelate. The addition of Ph2PPrPDI to FeBr2 resulted in bromide dissociation and the formation of [(Ph2PPrPDI)FeBr][Br]. Reduction of this precursor using excess sodium amalgam afforded (Ph2PPrPDI)Fe, which possesses an Fe(II) center that is supported by a dianionic PDI ligand. Similarly, reduction of a premixed solution of Ph2PPrPDI and CoCl2 yielded the cobalt analog, (Ph2PPrPDI)Co. EPR spectroscopy and density functional theory calculations revealed that this compound features a high-spin Co(I) center that is antiferromagnetically coupled to a PDI radical anion. The addition of Ph2PPrPDI to Ni(COD)2 resulted in ligand displacement and the formation of (Ph2PPrPDI)Ni, which was found to possess a pendent phosphine group. Single-crystal X-ray diffraction, CASSCF calculations, and EPR spectroscopy indicate that (Ph2PPrPDI)Ni is best described as having a Ni(II)-PDI2- configuration. The electronic differences between these compounds are highlighted, and a computational analysis of Ph2PPrPDI denticity has revealed the thermodynamic penalties associated with phosphine dissociation from 5-coordinate (Ph2PPrPDI)Mn, (Ph2PPrPDI)Fe, and (Ph2PPrPDI)Co.

A Pair of Cobalt(III/IV) Terminal Imido Complexes.

The reaction of the cobalt(I) complex [(TIMMNmes)CoI](BPh4) (2) (TIMMNmes=tris‐[2‐(3‐mesitylimidazolin‐2‐ylidene)methyl]amine) with 1‐adamantylazide yields the cobalt(III) imido complex [(TIMMNmes)CoIII(NAd)](BPh4) (3) with concomitant release of dinitrogen. The N‐anchor in diamagnetic 3 features an unusual, planar tertiary amine, which results from repulsive electrostatic interaction with the filled d(z2)‐orbital of the cobalt ion and negative hyperconjugation with the neighboring methylene groups. One‐electron oxidation of 3 with [FeCp2](OTf) provides access to the rare, high‐valent cobalt(IV) imido complex [(TIMMNmes)CoIV(NAd)](OTf)2 (4). Despite a half‐life of less than 1 h at room temperature, 4 could be isolated at low temperatures in analytically pure form. Single‐crystal X‐ray diffractometry and EPR spectroscopy corroborate the molecular structure and the d5 low‐spin, S=1/2 , electron configuration. A computational analysis of 4 suggests high covalency within the CoIV=NAd bond with non‐negligible spin density located at the imido moiety, which translates into substantial triplet nitrene character.

A Magnetically Robust Triplet Ground State Sulfur-Hydrocarbon Diradical Dication.

The one- and two-electron oxidation reactions of tetrathiolated di-tert-butylpyrene compound 1 with NO[Al(ORF)4] (ORF = OC(CF3)3) resulted in radical cation salt 1•+[Al(ORF)4]- and diradical dication salt 12+••·2[Al(ORF)4]-, respectively. Both salts were isolated as stable crystals and investigated by single-crystal X-ray diffraction, EPR spectroscopy, SQUID measurements, and UV-vis spectroscopy. The electron spin density is delocalized on one single sulfur-doped ring in 1•+ and on both sulfur-doped rings in 12+••. The diradical dication 12+•• features a robust triplet ground state, representing the first example of a high-spin sulfur-hydrocarbon diradical.

Stable, yet "naked", azo radical anion ArNNAr- and dianion ArNNAr2- (Ar = 4-CN-2,6-iPr2-C6H2) with selective CO2 activation.

Azo radical anion 1˙- and dianion 12- have been isolated by one- and two-electron reduction of the azo compound 1 (ArNNAr, Ar = 4-CN-2,6-iPr2-C6H2) with alkali metals, respectively. The reduced species have been characterized by single-crystal X-ray analysis, EPR, UV and FT-IR spectroscopy, as well as SQUID measurements. The filling of one and two electrons in the π* orbital of the N-N double bond of 1 leads to a half-double N-N bond in 1˙- and a single N-N bond in 12-. The uncoordinated nature of these reduced species enables them to activate CO2. The exposure of 1˙- solution to CO2 led to the formation of oxalate anion C2O42-, while that of 12- solution to CO2 afforded the hydrazine dicarboxylate dianion [1-2CO2]2-, which reversibly dissociated back to 1 and CO2 upon oxidation.

Early-Transition-Metal Complexes of Functionalized Nonagermanide Clusters: Synthesis and Characterization of [Cp2(MeCN)Ti(η1-Ge9{Si(TMS)3}3)] and K3[Cp2Ti(η1-Ge9{Si(TMS)3}2)2

Anionic clusters with a homoatomic [Ge9] core are species with Ge atoms in low oxidation states. In this study their reaction with early-transition-metal complexes was investigated. We report the syntheses of Ti(III) complexes of silylated [Ge9] Zintl clusters, which are rare examples of molecular complexes with Ge-Ti interactions. The neutral species [Cp2(MeCN)Ti(η1-Ge9{Si(TMS)3}3)] (1) was obtained by the reaction of K[Ge9{Si(TMS)3}3] with [Cp2TiCl]2 in toluene as dark orange crystals, whereas the reaction of K2[Ge9{Si(TMS)3}2] with [Cp2TiCl]2 in thf and subsequent recrystallization from toluene resulted in dark green crystals of K3[Cp2Ti(η1-Ge9{Si(TMS)3}2)2] (2). Compound 2 contains the trianion [Cp2Ti(η1-Ge9{Si(TMS)3}2)2]3- (2a), which can be described either as a [Cp2Ti]+-bridged [Ge9{Si(TMS)3}2]2- dimer or as a heavily distorted tetrahedral Ti(III) complex bearing two germanide cluster ligands. Both compounds display donor-acceptor interactions between single Ge vertex atoms of the [Ge9] clusters and Ti(III). Compounds 1 and 2 were characterized by single-crystal X-ray diffraction, EPR spectroscopy, and elemental analysis.

Electrochemically Driven Water Oxidation by a Highly Active Ruthenium-Based Catalyst.

The highly active ruthenium-based water oxidation catalyst [RuX (mcbp)(OHn )(py)2 ] [mcbp2- =2,6-bis(1-methyl-4-(carboxylate)benzimidazol-2-yl)pyridine; n=2, 1, and 0 for X=II, III, and IV, respectively], can be generated in a mixture of RuIII and RuIV states from either [RuII (mcbp)(py)2 ] or [RuIII (Hmcbp)(py)2 ]2+ precursors. The precursor complexes are isolated and characterized by single-crystal X-ray analysis, NMR, UV/Vis, EPR, and FTIR spectroscopy, ESI-HRMS, and elemental analysis, and their redox properties are studied in detail by electrochemical and spectroscopic methods. Unlike the parent catalyst [Ru(tda) (py)2 ] (tda2- =[2,2':6',2''-terpyridine]-6,6''-dicarboxylate), for which full transformation into the catalytically active species [RuIV (tda)(O)(py)2 ] could not be carried out, stoichiometric generation of the catalytically active Ru-aqua complex [RuX (mcbp)(OHn )(py)2 ] from the RuII precursor was achieved under mild conditions (pH 7.0) and short reaction times. The redox properties of the catalyst were studied and its activity for electrocatalytic water oxidation was evaluated, reaching a maximum turnover frequency (TOFmax ) of around 40 000 s-1 at pH 9.0 (from foot-of-the-wave analysis), which is comparable to the activity of the state-of-the-art catalyst [RuIV (tda)(O)(py)2 ].

Mononuclear manganese(iii) complexes with reduced imino nitroxide radicals by single-electron transfer and intermolecular hydrogen bonds as an intramolecular structural driving force.

Manganese(iii) complexes were synthesized by one-electron transfer from a Mn(ii) ion to the imino nitroxide radical 2-(2-imidazolyl)-4,4,5,5-tetramethylimidazoline-1-oxyl (IMImH) in methanol. After the manganese ions attained the +III oxidation state, the imino nitroxide radicals were found to be irreversibly reduced in the complexes. Depending on the synthesis conditions, two complexes differing by their counter-anions were isolated as single crystals. These are [Mn(IMHIm)2(MeOH)2]ClO4·H2O (1) and [Mn(IMHIm)2(MeOH)2]PF6 (2), which crystallize in the monoclinic P21/n and triclinic P1[combining macron] space groups, respectively. The two complexes show Jahn-Teller distortions typical of Mn(iii) centres and only reduced radicals are coordinated, as indicated by the N-O bond lengths and electroneutrality. In addition, the crystal structure analyses reveal two intermolecular hydrogen bonding networks. One involves counter-anions, water molecules and reduced radicals, and the other involves coordinated methanol molecules and imidazole moieties. These intermolecular interactions are driving forces that stabilize the two complexes. They also suggest that the tautomer is in the amino imine-oxide form after reduction of the radical and reveal the deprotonation of the imidazole ring, which is required for electroneutrality. This assessment is supported by single-crystal X-ray diffraction, EPR and Raman spectroscopy as well as magnetic and electrochemical studies.

Stable Boron Dithiolene Radicals.

Whereas low-temperature (-78 °C) reaction of the lithium dithiolene radical 1. with boron bromide gives the dibromoboron dithiolene radical 2. , the parallel reaction of 1. with (C6 H11 )2 BCl (0 °C) affords the dicyclohexylboron dithiolene radical 3. . Radicals 2. and 3. were characterized by single-crystal X-ray diffraction, UV/Vis, and EPR spectroscopy. The nature of these radicals was also probed computationally. Under mild conditions, 3. undergoes unexpected thiourea-mediated B-C bond activation to give zwitterion 4, which may be regarded as an anionic dithiolene-modified carbene complex of the sulfenyl cation RS+ (R=cyclohexyl).

A structurally-characterized peroxomanganese(iv) porphyrin from reversible O2 binding within a metal-organic framework.

The role of peroxometal species as reactive intermediates in myriad biological processes has motivated the synthesis and study of analogous molecular model complexes. Peroxomanganese(iv) porphyrin complexes are of particular interest, owing to their potential ability to form from reversible O2 binding, yet have been exceedingly difficult to isolate and characterize in molecular form. Alternatively, immobilization of metalloporphyrin sites within a metal-organic framework (MOF) can enable the study of interactions between low-coordinate metal centers and gaseous substrates, without interference from bimolecular reactions and axial ligation by solvent molecules. Here, we employ this approach to isolate the first rigorously four-coordinate manganese(ii) porphyrin complex and examine its reactivity with O2 using infrared spectroscopy, single-crystal X-ray diffraction, EPR spectroscopy, and O2 adsorption analysis. X-ray diffraction experiments reveal for the first time a peroxomanganese(iv) porphyrin species, which exhibits a side-on, η2 binding mode. Infrared and EPR spectroscopic data confirm the formulation of a peroxomanganese(iv) electronic structure, and show that O2 binding is reversible at ambient temperature, in contrast to what has been observed in molecular form. Finally, O2 gas adsorption measurements are employed to quantify the enthalpy of O2 binding as hads = -49.6(8) kJ mol-1. This enthalpy is considerably higher than in the corresponding Fe- and Co-based MOFs, and is found to increase with increasing reductive capacity of the MII/III redox couple.

Organosilicon Radicals with Si-H and Si-Me Bonds from Commodity Precursors.

The cyclic alkyl(amino) carbene (cAAC) stabilized biradicals of composition (cAAC)2SiH2 (1), (cAAC)SiMe2-SiMe2(cAAC) (2), and (cAAC)SiMeCl-SiMeCl(cAAC) (3) have been isolated as molecular species. All the compounds are stable at room temperature for more than 6 months under inert conditions in the solid state. All radical species were fully characterized by single-crystal X-ray structure analysis and EPR spectroscopy. Furthermore, the structure and bonding of compounds 1-3 have been investigated by theoretical methods. Compound 1 contains the SiH2 moiety and this is the first instance, where we have isolated 1 without an acceptor molecule.

Investigation into the Effects of a Trigonal-Planar Ligand Field on the Electronic Properties of Lanthanide(II) Tris(silylamide) Complexes (Ln = Sm, Eu, Tm, Yb).

In recent work we have reported the synthesis and physical properties of near-linear Ln(II) (Ln = lanthanide) complexes utilizing the bulky bis(silylamide) {N(SiiPr3)2}. Herein, we synthesize trigonal-planar Ln(II) complexes by employing a smaller bis(silylamide), {N(SitBuMe2)2} (N**), to study the effects of this relatively rare Ln geometry/oxidation state combination on the magnetic and optical properties of complexes. We show that the charge-separated trigonal-planar Ln(II) complexes [K(2.2.2-cryptand)][Ln(N**)3] (Ln = Sm (1), Eu (2), Tm (3), Yb (4)) can be prepared by the reaction of 1.5 equiv of [{K(N**)}2] with LnI2THF2 (Ln = Sm, Yb) or LnI2 (Ln = Eu, Tm) and 1 equiv of 2.2.2-cryptand in Et2O. Complex 3 is the first structurally characterized trigonal-planar Tm(II) complex. In the absence of 2.2.2-cryptand, [K(DME)3][Sm(N**)3] (5) and [Ln(N**)2(μ-N**)K(toluene)2] (Ln = Sm (6), Eu (7)) were isolated in the presence of DME (dimethoxyethane) or toluene, respectively. The 1:1 reaction of [{K(N**)}2] with LnI2THF2 (Ln = Sm, Yb) in THF gave the four-coordinate pseudo-tetrahedral Lewis base adducts [Ln(N**)2(THF)2] (Ln = Sm (8), Yb (9)) and the cyclometalated complex [Yb(N**){N(SitBuMe2)(SitBuMeCH2)}(THF)] (10). Complexes 1-10 have been characterized as appropriate by single-crystal XRD, magnetic measurements, multinuclear NMR, EPR, and electronic spectroscopy, together with CASSCF-SO and DFT calculations. The physical properties of 1-4 are compared and contrasted with those of closely related near-linear Ln(II) bis(silylamide) complexes.

Combining EPR spectroscopy and X-ray crystallography to elucidate the structure and dynamics of conformationally constrained spin labels in T4 lysozyme single crystals

Electron paramagnetic resonance (EPR) spectroscopy in combination with site-directed spin labeling is used to investigate the structure and dynamics of conformationally constrained spin labels in T4 lysozyme single crystals. Within a single crystal, the oriented ensemble of spin bearing moieties results in a strong angle dependence of the EPR spectra. A quantitative description of the EPR spectra requires the determination of the unit cell orientation with respect to the sample tube and the orientation of the spin bearing moieties within the crystal lattice. Angle dependent EPR spectra were analyzed by line shape simulations using the stochastic Liouville equation approach developed by Freed and co-workers and an effective Hamiltonian approach. The gain in spectral information obtained from the EPR spectra of single crystalline samples taken at different frequencies, namely the X-band and Q-band, allows us to discriminate between motional models describing the spectra of isotropic solutions similarly well. In addition, it is shown that the angle dependent single crystal spectra allow us to identify two spin label rotamers with very similar side chain dynamics. These results demonstrate the utility of single crystal EPR spectroscopy in combination with spectral line shape simulation techniques to extract valuable dynamic information not readily available from the analysis of isotropic systems. In addition, it will be shown that the loss of electron density in high resolution diffraction experiments at room temperature does not allow us to conclude that there is significant structural disorder in the system.

Synthesis and crystal structures of novel copper(II) complexes with glycine and substituted phenanthrolines: reactivity towards DNA/BSA and in vitro cytotoxic and antimicrobial evaluation.

New copper(II) complexes-dimeric-[Cu(nphen)(gly)(H2O)]+ (1) and [Cu(dmphen)(gly)(NO3)(H2O)] (2) (nphen=5-nitro-1,10-phenanthroline, dmphen=4,7-dimethyl-1,10-phenanthroline, and gly=glycine)-have been synthesized and characterized by CHN analysis, single-crystal X-ray diffraction techniques, FTIR, EPR spectroscopy, and cyclic voltammetry. The CT-DNA-binding properties of these complexes have been investigated by thermal denaturation measurements and both absorption and emission spectroscopy. The DNA cleavage activity of these complexes has been studied on supercoiled pUC19 plasmid DNA by gel electrophoresis experiments in the absence and presence of H2O2. Furthermore, the interaction of these complexes with bovine serum albumin (BSA) has been investigated using absorption and emission spectroscopy. The thermodynamic parameters, free-energy change (ΔG), enthalpy change (ΔH), and entropy change (ΔS) for BSA+complexes 1 and 2 systems have been calculated by the van't Hoff equation at three different temperatures (293.2, 303.2, and 310.2K). The distance between the BSA and these complexes has been determined using fluorescence resonance energy transfer (FRET). Conformational changes of BSA have been observed using the synchronous fluorescence technique. In addition, in vitro cytotoxicities of these complexes on tumor cell lines (Caco-2, A549, and MCF-7) and healthy cells (BEAS-2B) have been examined. The antimicrobial activity of the complexes has also been tested on certain bacteria cells. The effect of mono and dimeric in the above complexes is presented and discussed. New copper(II) complexes-dimeric-[Cu(nphen)(gly)(H2O)]+ (1) and [Cu(dmphen)(gly) (NO3)(H2O)] (2) (nphen = 5-nitro-1,10-phenanthroline, dmphen = 4,7-dimethyl-1,10-phenanthroline and gly = glycine)-have been synthesized and characterized by CHN analysis, single-crystal X-ray diffraction techniques, FTIR and EPR spectroscopy. They have been tested for their in vitro DNA/BSA interactions by the spectroscopic methods. These complexes exhibited higher cytotoxic and antimicrobial activities. Complex 1 shows better DNA / BSA interactions in comparison to complex 2.

Dioxygen binding at a four-coordinate cobaltous porphyrin site in a metal–organic framework: structural, EPR, and O2adsorption analysis

The binding of O2at a four-coordinate cobaltous porphyrin site within a metal–organic framework is examined through single-crystal X-ray diffraction, EPR spectroscopy, and O2adsorption measurements.