Effect of the ancillary ligands on the binding of ruthenium(II) complexes [Ru(dmp)2(MCMIP)]2+ and [Ru(dmb)2(MCMIP)]2+ with DNA

Two polypyridine ruthenium(II) complexes, [Ru(dmp)₂(MCMIP)]²⁺ (1) (MCMIP = 2-(6-methyl-3-chromonyl)imidazo[4,5-f][1,10]-phenanthroline, dmp = 2,9-dimethyl-1,10-phenanthroline) and [Ru(dmb)₂(MCMIP)]²⁺ (2) (dmb = 4,4′-dimethyl-2,2′-bipyridine), have been synthesized and characterized by elemental analysis, ES-MS and ¹H NMR. The DNA-binding behaviors of these complexes were investigated by electronic absorption titration, fluorescence spectroscopy, viscosity measurements and thermal denaturation. The results show that 1 and 2 effectively bind to CT-DNA; the DNA-binding affinities are closely related to the ancillary ligand.     

Dehydration of peptide [M + H]+ ions in the gas phase

The loss of water from protonated peptides was studied using [¹⁸O]-labeling of the C-terminal carboxyl group. The structures (including the location of the isotopic label) of first-generation product ions were examined by sequential product ion scanning (MS³ and MS⁴) using a hybrid sector/quadrupole mass spectrometer. Water loss may involve carboxylic acid groups, side-chain hydroxyls, or peptide backbone oxygens. Although one of these three pathways often predominates, more than one dehydration route can be operative for a single peptide structure. When peptide backbone oxygen is lost, the dehydration can occur at one or two primary sites along the backbone, with the location of the site(s) varying among peptides. When water loss involves the C-terminal carboxyl group, the resulting ion may undergo extensive intraionic oxygen isotope exchange. This evidence for complex intraionic interactions further emphasizes the significance of gas-phase conformation in determining the fragmentations of peptide ions.     

Infrared spectroscopy of gas-phase Cr+ coordination complexes: determination of binding sites and electronic states

Infrared spectra were recorded for a series of gas-phase Cr+ complexes using infrared multiphoton dissociation (IRMPD) in a Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometer. The functionalized aromatic ligands (acetophenone, anisole, aniline, and dimethyl aniline) offer a choice of either aromatic ring-pi or n-donor-base binding sites. Use of the FELIX free electron laser light source allowed convenient, rapid scanning of the chemically informative wavelength range from approximately 500 to 1800 cm(-1), which in many cases characterized the preferred site of metal binding, as well as the electronic spin state of the complex. Mono-complex ions, Cr+(ligand), for anisole, aniline, and dimethyl aniline and bis-complex ions, Cr+(ligand)(2), for anisole, aniline, and acetophenone were produced by ligand attachment to laser-desorbed Cr+ ions in the FT-ICR cell. The photodissociation yields plotted as a function of wavelength were interpreted as approximations to the infrared absorption spectra and were compared with computed spectra of different possible geometries and spin states. Clear-cut diagnostic features in the spectra of the acetophenone, anisole, and aniline complexes showed the sites of Cr+ attachment to be the carbonyl oxygen site for acetophenone (bis-complex) and the ring-pi site for anisole and aniline (both mono- and bis-complexes). The bis-complexes of aniline and anisole are low-spin (probably doublet) states, while the mono-complexes of these same ligands are high-spin (sextet) states. The dimethyl aniline complex gave a cluttered spectrum in poor agreement with calculations, which may reflect a mixture of binding-site isomers in this case.     

Interaction studies of DNA binding of ruthenium(II) mixed-ligand complexes: [Ru(phen)2(dtmi)]2+ and [Ru(phen)2(dtni)]2+

Two new ligands, 3-(pyrazin-2-yl)-as-triazino[5,6-f]-5-methoxylisatin (dtmi), 3-(pyrazin-2-yl)-as-triazino[5,6-f]-5-nitroisatin (dtni) and their ruthenium(II) complexes [Ru(phen)2(dtmi)](ClO4)2 (1) and [Ru(phen)2(dtni)](ClO4)2 (2) have been prepared and characterized by elemental analysis, FAB-MS, ES-MS and 1H NMR. The DNA-binding behaviors of complexes have been studied by spectroscopic titration, viscosity measurements, thermal denaturation and circular dichromism (CD). The results indicate that the complexes 1 and 2 interact with calf thymus DNA (CT-DNA) by intercalative mode. The DNA-binding affinity of the complexes 2 is larger than that complex 1 does.     

Synthesis,characterization, duplex-DNA interactions,and anticancer activities of novel octahedral [Ni(phen)2(dppz-idzo)]2+ and [Co(phen)2(dppz-idzo)]3+ complexes

Two new octahedral [Ni(phen)₂(dppz-idzo)]²⁺ and [Co(phen)₂(dppz-idzo)]³⁺ complexes have been synthesized and characterized by CHN analysis, electrospray ionization-MS, nuclear magnetic resonance, and UV–Vis spectra. The DNA-binding ability of these complexes was spectrophotometrically, hydrodynamically, and electrophoretically evaluated which indicated that they strongly intercalate into the DNA double helix, and that both induced severe DNA damage in the presence of peroxide. The complexes also showed strong antiproliferative effect against HepG2 and MDA-MB-231 cells. By contrast, they were found to be inactive against the MCF-7 cell line. The ligand itself was found to be inactive against the cells tested.     

Generation and reactivity of enantiomeric (BINOLato)Ni+ complexes with chiral secondary alcohols in the gas phase

In the presence of secondary alcohols, electrospray ionization of dilute methanolic solutions of nickel(II) salts and 1,1'-bis-2-naphthol (BINOL) leads to complexes of the formal composition [(BINOLato)Ni(CH3CH(OH)R)]+ (BINOLato refers to a singly deprotonated (R)- or (S)-1,1'-bis-2-naphthol ligand; R=CH3, C2H5, n-C3H7, n-C4H9, n-C5H11, n-C6H13, c-C6H11, and C6H5). Upon collision-induced dissociation, each mass-selected nickel complex either loses the entire secondary alcohol ligand or undergoes bond activation followed by elimination of the corresponding ketone, as revealed by deuterium labeling. When enantiomeric BINOLato ligands (R or S) are combined with chiral secondary alcohols (R or S), differences in the branching ratios between these channels for the two stereoisomers of the secondary alcohols provide insight into the chiral discrimination operative in the C--H- and O--H-bond activation processes. For saturated alkan-2-ols, the chiral discrimination is low, and if any preference is observed at all, ketone elimination from the homochiral complexes (R,R and S,S) is slightly favored. In contrast, the diastereomeric (BINOLato)Ni+ complexes of 1-phenylethanol exhibit preferential ketone losses for the heterochiral systems (S,R and R,S).     

Ru(phen)2(PHEHAT)]2+ and [Ru(phen)2(HATPHE)]2+: two ruthenium(II) complexes with the same ligands but different photophysics and spectroelectrochemistry

The properties of two mononuclear Ru(II) complexes formed with the extended planar ligand PHEHAT depend drastically on the chelation site by the metallic ion. When the chelation takes place on the HAT site of the ligand (case of the novel complex [Ru(phen)2(HATPHE)]2+), the emission behavior is quite similar to that of [Ru(phen)2(HAT)]2+. In contrast, when the chelation is on the phen motif of the ligand (case of [Ru(phen)2(PHEHAT)]2+), the spectroscopic (absorption and emission) and electrochemical data for the complex do not obey the linear spectroelectrochemical correlation and the emission behavior is comparable to that of the extensively studied dppz complex ([Ru(phen/bpy)2(dppz)]2+). Thus, for [Ru(phen)2(PHEHAT)]2+, the emission lifetimes and intensities as a function of temperature exhibit a maximum for nitrile solvents. However, in contrast to the dppz case, at least three different states (two emitting and one dark) participate in the deactivation with different contributions depending on the temperature. These different contributions explain the observed maximum. Moreover, the fact that the solvent is liquid or frozen also influences the nature of the luminescent species.     

Synthesis,characterization, and DNA-binding of [Co(phen)2(CPIA)]3+, [Co(phen)2(BIP)]3+, and [Co(phen)2(CIP)]3+

Three ligands, 2-(3-(carboxymethyl)-1,10-phenanthroline-[5,6-d]imidazole-1-yl)acetate (CPIA), 2-(benzo[d][1,3]dioxol-4-yl)-1H-imidazo[4,5-f][1,10]phenanthroline (BIP), and 2-(9H-carbazol-3-yl)-1H-imidazo[4,5-f][1,10]phenanthroline (CIP), and their complexes, [Co(phen)₂(CPIA)]³⁺ (1) (phen = 1,10-phenanthroline), [Co(phen)₂(BIP)]³⁺ (2), and [Co(phen)₂(CIP)]³⁺ (3), have been synthesized and characterized. Binding of the three complexes with calf thymus DNA (CT-DNA) has been investigated by spectroscopic methods, cyclic voltammetry, and viscosity measurements. The three complexes bind to DNA through an intercalative mode, and the size and shape of the intercalative ligands have significant effects on the binding affinity of complexes to CT-DNA.     

Nature of metal binding sites in Cu(II) complexes with histidine and related N-coordinating ligands, as studied by EXAFS

Knowledge of the complexes formed by N-coordinating ligands and Cu(II) ions is of relevance in understanding the interactions of this ion with biomolecules. Within this framework, we investigated Cu(II) complexation with mono- and polydentate ligands, such as ammonia, ethylenediamine (en), and phthalocyanine (Pc). The obtained Cu-N coordination distances were 2.02 A for [Cu(NH(3))(4)](2+), 2.01 A for [Cu(en)(2)](2+), and 1.95 A for CuPc. The shorter bond distance found for CuPc is attributed to the macrocyclic effect. In addition to the structure of the first shell, information on higher coordination shells of the chelate ligands could be extracted by EXAFS, thus allowing discrimination among the different coordination modes. This was possible due to the geometry of the complexes, where the absorbing Cu atoms are coplanar with the four N atoms forming the first coordination shell of the complex. For this reason multiple scattering contributions become relevant, thus allowing determination of higher shells. This knowledge has been used to gain information about the structure of the 1:2 complexes formed by Cu(II) ions with the amino acids histidine and glycine, both showing a high affinity for Cu(II) ions. The in-solution structure of these complexes, particularly that with histidine, is not clear yet, probably due to the various possible coordination modes. In this case the square-planar arrangements glycine-histamine and histamine-histamine as well as tetrahedral coordination modes have been considered. The obtained first-shell Cu-N coordination distance for this complex is 1.99 A. The results of the higher shells EXAFS analysis point to the fact that the predominant coordination mode is the so-called histamine-histamine one in which both histidine molecules coordinate Cu(II) cations through N atoms from the amino group and from the imidazole ring.     

Vibrational spectroscopy of Ni+ (benzene)n complexes in the gas phase

Ni+ (benzene)n (n = 1-6) and Ni+ (benzene)n Ar(1,2) (n = 1,2) are produced by laser vaporization in a pulsed nozzle cluster source. The clusters are mass selected and studied by infrared laser photodissociation spectroscopy in a reflectron time-of-flight mass spectrometer. The excitation laser is an OPO/OPA system that produces tunable IR in the C-H stretching region of benzene. Photodissociation of Ni+ (benzene)n complexes occurs by the elimination of intact neutral benzene molecules, while Ni+ (benzene)n Ar(1,2) complexes lose Ar. This process is enhanced on resonances, and the vibrational spectrum is obtained by monitoring the fragment yield versus the infrared wavelength. Vibrational bands in the 2700-3300 cm(-1) region are characteristic of the benzene molecular moiety with systematic shifts caused by the metal bonding. A dramatic change in the IR spectrum is seen at n = 3 and is attributed to the presence of external benzene molecules acting as solvent molecules in the cluster. The results of previous theoretical calculations are employed to investigate the structures, energetics, and vibrational frequencies of these complexes. The mono-benzene complex is found to have a C2v structure, with benzene distorted by the metal pi-bonding. The di-benzene complex is found to have a D2h structure, with both benzenes distorted. The comparison between experiment and theory provides intriguing new insight into the bonding in these prototypical pi-bonded organometallic complexes.     

Mixed ligand complexes of [Pd(terpy)(H2O)]2+ with some selected amino acids,peptides, DNA and related ligands

Stability constants of the ternary palladium(II) complexes of triamine 2,2′:6′,2″-terpyridine (terpy) and some amino acids, peptides, DNA constituents or thiols were determined at 25 °C and at constant 0.1 mol dm⁻³ ionic strength, adjusted using NaNO₃. The coordination sites are pH-dependent. The results show the formation of binuclear species, 210. The speciation diagrams of various complex species were evaluated as a function of pH. Good correlations were found between the stability constants of the complexes and basicity of ligands.     

Ligand field photofragmentation spectroscopy of [Ag(L)N]2+ complexes in the gas phase: experiment and theory

Experiments have been undertaken to record photofragmentation spectra from a series of [Ag(L)N]2+ complexes in the gas phase. Spectra have been obtained for silver(II) complexed with the ligands (L): acetone, 2-pentanone, methyl-vinyl ketone, pyridine, and 4-methyl pyridine (4-picoline) with N in the range of 4-7. A second series of experiments using 1,1,1,3-fluoroacetone, acetonitrile, and CO2 as ligands failed to show any evidence of photofragmentation. Interpretation of the experimental data has come from time-dependent density functional theory (TDDFT), which very successfully accounts for trends in the spectra in terms of subtle differences in the properties of the ligands. Taking a sample of three ligands, acetone, pyridine, and acetonitrile, the calculations show all the spectral transitions to involve ligand-to-metal charge transfer, and that wavelength differences (or lack of spectra) arise from small changes in the energies of the molecular orbitals concerned. The calculations account for an absence in the spectra of any effects due to Jahn-Teller distortion, and they also reveal structural differences between complexes where the coordinating atom is either oxygen or nitrogen that have implications for the stability of silver(II) compounds. Where possible, comparisons have also been made with the physical properties of condensed phase silver(II) complexes.     

Vibrational spectroscopy of mass-selected [UO2(ligand)n]2+ complexes in the gas phase: comparison with theory

The gas-phase infrared spectra of discrete uranyl ([UO2]2+) complexes ligated with acetone and/or acetonitrile were used to evaluate systematic trends of ligation on the position of the O=U=O stretch and to enable rigorous comparison with the results of computational studies. Ionic uranyl complexes isolated in a Fourier transform ion cyclotron resonance mass spectrometer were fragmented via infrared multiphoton dissociation using a free electron laser scanned over the mid-IR wavelengths. The asymmetric O=U=O stretching frequency was measured at 1017 cm(-1) for [UO2(CH3COCH3)2]2+ and was systematically red shifted to 1000 and 988 cm(-1) by the addition of a third and fourth acetone ligand, respectively, which was consistent with increased donation of electron density to the uranium center in complexes with higher coordination number. The values generated computationally using LDA, B3LYP, and ZORA-PW91 were in good agreement with experimental measurements. In contrast to the uranyl frequency shifts, the carbonyl frequencies of the acetone ligands were progressively blue shifted as the number of ligands increased from two to four and approached that of free acetone. This observation was consistent with the formation of weaker noncovalent bonds between uranium and the carbonyl oxygen as the extent of ligation increases. Similar trends were observed for [UO2(CH3CN)n]2+ complexes, although the uranyl asymmetric stretching frequencies were greater than those measured for acetone complexes having equivalent coordination, which is consistent with the fact that acetonitrile is a weaker nucleophile than is acetone. This conclusion was confirmed by the uranyl stretching frequencies measured for mixed acetone/acetonitrile complexes, which showed that substitution of one acetone for one acetonitrile produced a modest red shift of 3-6 cm(-1).     

Tuning of the [Cu3(mu-O)]4+/5+ redox couple: spectroscopic evidence of charge delocalization in the mixed-valent [Cu3(mu-O)]5+ species

Trinuclear Cu (II)-complexes of formula [Cu (II) 3(mu 3-E)(mu-4-R-pz) 3X 3] (+/- n ), E = O and OH; R = H, Cl, Br, CH(O) and NO 2; X = Cl, NCS, CH 3COO, and py, have been synthesized and characterized and the effect of substitution of terminal ligands, as well as 4-R-groups, in the one-electron oxidation process has been investigated by cyclic voltammetry. In situ UV-vis-NIR spectroelectrochemical characterization of the mixed valence Cu 3 (7+)-complex [Cu 3(mu 3-O)(mu-pz) 3Cl 3] (-) revealed an intervalence charge transfer band at 9550 cm (-1) (epsilon = 2600 cm (-1) M (-1)), whose analysis identifies this species as a delocalized, Robin-Day class-III system, with an electronic coupling factor, H ab, of 4775 cm (-1).     

Symmetric and asymmetric dinuclear manganese(IV) complexes possessing a [MnIV2(mu-O)2(muO2CMe)]3+ core and terminal Cl- ligands

The synthesis of new dinuclear manganese(IV) complexes possessing the [Mn(IV)(2)(mu-O)(2)(mu-O(2)CMe)](3+) core and containing halide ions as terminal ligands is reported. [Mn(2)O(2)(O(2)CMe)Cl(2)(bpy)(2)](2)[MnCl(4)] (1; bpy = 2,2'-bipyridine) was prepared by sequential addition of [MnCl(3)(bpy)(H(2)O)] and (NBzEt(3))(2)[MnCl(4)] to a CH(2)Cl(2) solution of [Mn(3)O(4)(O(2)CMe)(4)(bpy)(2)]. The complex [Mn(IV)(2)O(2)(O(2)CMe)Cl(bpy)(2)(H(2)O)](NO(3))(2) (2) was obtained from a water/acetic acid solution of MnCl(2).4H(2)O, bpy, and (NH(4))(2)[Ce(NO(3))(6)], whereas the [Mn(IV)(2)O(2)(O(2)CR)X(bpy)(2)(H(2)O)](ClO(4))(2) [X = Cl(-) and R = Me (3), Et (5), or C(2)H(4)Cl (6); and X = F(-), R = Me (4)] were prepared by a slightly modified procedure that includes the addition of HClO(4). For the preparation of 4, MnF(2) was employed instead of MnCl(2).4H(2)O. [Mn(2)O(2)(O(2)CMe)Cl(2)(bpy)(2)](2)[MnCl(4)].2CH(2)Cl(2) (1.2CH(2)Cl(2)) crystallizes in the monoclinic space group C2/c with a = 21.756(2) A, b = 12.0587(7) A, c = 26.192(2) A, alpha = 90 degrees, beta = 111.443(2) degrees, gamma = 90 degrees, V = 6395.8(6) A(3), and Z = 4. [Mn(2)O(2)(O(2)CMe)Cl(H(2)O)(bpy)(2)](NO(3))(2).H(2)O (2.H(2)O) crystallizes in the triclinic space group Ponemacr; with a = 11.907(2) A, b = 12.376(2) A, c = 10.986(2) A, alpha = 108.24(1) degrees, beta = 105.85(2) degrees, gamma = 106.57(1) degrees, V = 1351.98(2) A(3), and Z = 2. [Mn(2)O(2)(O(2)CMe)Cl(H(2)O)(bpy)(2)](ClO(4))(2).MeCN (3.MeCN) crystallizes in the triclinic space group Ponemacr; with a = 11.7817(7) A, b = 12.2400(7) A, c = 13.1672(7) A, alpha = 65.537(2) degrees, beta = 67.407(2) degrees, gamma = 88.638(2) degrees, V = 1574.9(2) A(3), and Z = 2. The cyclic voltammogram (CV) of 1 exhibits two processes, an irreversible oxidation of the [MnCl(4)](2)(-) at E(1/2) approximately 0.69 V vs ferrocene and a reversible reduction at E(1/2) = 0.30 V assigned to the [Mn(2)O(2)(O(2)CMe)Cl(2)(bpy)(2)](+/0) couple (2Mn(IV) to Mn(IV)Mn(III)). In contrast, the CVs of 2 and 3 show only irreversible reduction features. Solid-state magnetic susceptibility (chi(M)) data were collected for complexes 1.1.5H(2)O, 2.H(2)O, and 3.H(2)O in the temperature range 2.00-300 K. The resulting data were fit to the theoretical chi(M)T vs T expression for a Mn(IV)(2) complex derived by use of the isotropic Heisenberg spin Hamiltonian (H = -2JS(1)S(2)) and the Van Vleck equation. The obtained fit parameters were (in the format J/g) -45.0(4) cm(-)(1)/2.00(2), -36.6(4) cm(-)(1)/1.97(1), and -39.3(4) cm(-)(1)/1.92(1), respectively, where J is the exchange interaction parameter between the two Mn(IV) ions. Thus, all three complexes are antiferromagnetically coupled.     

[RhCl(CO)(PPh3)]2. A precursor for the synthesis of cationic rhodium complexes with nitrogen donor ligands

Summary The use of [RhCl(CO)(PPh₃)]₂ as a precursor for the synthesis of complexes of the types [Rh(CO)L₂(PPh₃)]A (A = [ClO₄]^– or [BPh₄]^–; L = pyridine type ligand) and [Rh(CO)(L-L)(PPh₃)]A (A = [ClO₄]^– or [BPh₄]^–; L-L = bidentate nitrogen donor) and the preparation of several complexes of the types [Rh(CO)L(PPh₃){P(p-RC₆H₄)₃}]BPh₄ and [Rh(CO)(phen)(PPh₃){P(p-RC₆H₄)₃}]A (A = [ClO₄]^– or [BPh₄]^–; R = H or Me) is described.Author to whom all correspondence should be directed.     

Vibrational spectroscopy of anionic nitrate complexes of UO22+ and Eu3+ isolated in the gas phase

Wavelength-selective infrared multiple photon photo-dissociation (IRMPD) was used to generate spectra of anionic nitrate complexes of UO(2)(2+) and Eu(3+) in the mid-infrared region. Similar spectral patterns were observed for both species, including splitting of the antisymmetric O-N-O stretch into high and low frequency components with the magnitude of the splitting consistent with attachment of nitrate to a strong Lewis acid center. The frequencies measured for [UO(2)(NO(3))(3)](-) were within a few cm(-1) of those measured in the condensed phase, the best agreement yet achieved for a comparison of IRMPD with condensed phase absorption spectra. In addition, experimentally-determined values were in good general agreement with those predicted by DFT calculations, especially for the antisymmetric UO(2) stretch. The spectrum from the [UO(2)(NO(3))(3)](-) was compared with that of [Eu(NO(3))(4)](-), which showed that nitrate was bound more strongly to the Eu(3+) metal center, consistent with its higher charge. The spectrum of a unique uranyl-oxo species having an elemental composition [UO(9)N(2)](-) was also acquired, that contained nitrate absorptions suggestive of a [UO(2)(NO(3))(2)(O)](-) structure; the spectrum lacked bands indicative of nitrite and superoxide that would be indicative of an alternative [UO(2)(NO(3))(NO(2))(O(2))](-) structure.     

Porphyrin complexes containing coordinated BOB groups: synthesis, chemical reactivity and the structure of [BOB(tpClpp)]2+

The reactions of boron halides with free base porphyrins under conditions where partial hydrolysis of the boron halides can occur give diboron porphyrin complexes containing BOB moieties in which each boron is bonded to two porphyrin nitrogen atoms. BF(3).OEt(2) with H(2)(por) gives B(2)OF(2)(por) (por = tpp, ttp, tpClpp, oep) which has an asymmetric structure in which one boron lies in the porphyrin plane (B(ip)) while the other lies above it (B(oop)). BCl(3).MeCN with H(2)(por) gives B(2)O(2)(BCl(3))(2)(por) which contains a four-membered B(2)O(2) ring and is stable only in the presence of excess BCl(3). BBr(3) with Li(2)(tpClpp) gives the dicationic complex [B(2)O(tpClpp)](2+) as its [BBr(4)](-) salt, and is the first example of a boron porphyrin containing three-coordinate boron to be structurally characterised. B(2)O(2)(BCl(3))(2)(por) can be chromatographed on basic alumina to give the hydroxyboron complex B(2)O(OH)(2)(por), which is deduced from its NMR spectra and DFT calculations to have a structure analogous to B(2)OF(2)(por). The OH protons are shifted upfield to near delta -4 (B(oop)-OH) and -10 (B(ip)-OH) by the diamagnetic porphyrin ring current. The reaction of either B(2)O(2)(BCl(3))(2)(por) or B(2)O(OH)(2)(por) (por = ttp, tpClpp) with alcohols (ROH, R = Et, 4-C(6)H(4)CH(3)) gives B(2)O(OR)(2)(por), which can in turn be converted to B(2)O(OR)(OH)(por) by repeated chromatography. The reaction of PhBCl(2) with H(2)(por) (por = ttp, tpClpp) gives B(2)O(Ph)(OH)(por) which has been characterised by spectroscopy in concert with DFT calculations. It is a further example of the B(2)OF(2)(por) structural type, in which the phenyl group is coordinated to the out-of-plane boron and the OH group to the in-plane boron, as are its derivatives B(2)O(Ph)(X)(tpClpp) (X = F, OEt). Steric drivers for the facile hydrolysis of haloboron porphyrins relative to their dipyrromethene and expanded porphyrin counterparts are discussed.     

Acetate and acetamide complexes of [Ni(Me4[12]aneN4)]PF6: a tale of two ligands

Although there are many examples of acetate complexes, acetamide complexes are virtually unknown. A side‐by‐side comparison in (acetato‐κ²O,O′)(1,4,7,10‐tetramethyl‐1,4,7,10‐tetraazacyclododecane‐κ⁴N)nickel(II) hexafluoridophosphate, [Ni(C₂H₃O₂)(C₁₂H₂₈N₄)]PF₆, (1), and (acetamidato‐κ²O,O′)(1,4,7,10‐tetramethyl‐1,4,7,10‐tetraazacyclododecane‐κ⁴N)nickel(II) hexafluoridophosphate, [Ni(C₂H₄NO)(C₁₂H₂₈N₄)]PF₆, (2), shows the steric equivalence between these two ligands, suggesting that acetamide could be considered as a viable acetate replacement for electronic tuning.