TY - JOUR
T1 - Synthesis, structure, and solution NMR studies of cyanide-copper(II) and cyanide-bridged iron(III)-copper(II) complexes
AU - Corsi, Daniele M.
AU - Murthy, Narasimha N.
AU - Young, Victor G.
AU - Karlin, Kenneth D.
PY - 1999/1/1
Y1 - 1999/1/1
N2 - A range of small molecules, such as cyanide, are known to bind and/or inhibit the active site of the heme-copper oxidase enzymes. As such, model studies are aimed at elucidating ligand binding modes and their subsequent impact on spectroscopic properties of derived complexes. We describe here the isolation and characterization of two compounds containing the Fe-CN-Cu moiety, [(py)(F8-TPP)FeIII-CN-CuII(TMPA)]2+ (5) and [(F8-TPP)-FeIII-(CN)2-{Cu II(TMPA)}2]3+ (6) [py = pyridine, TMPA = tris(2-pyridylmethyl)amine, and (F8-TPP) = tetrakis-(2,6-difluorophenyl)porphyrinate(2-)]. [CuII(TMPA)(CH3CN)](ClO4)2 and [(py)(F8-TPP)FeIII(CN)] (3) react to yield 5, while 6 is formed by combination of [CuII(TMPA)(CN)]PF6 (2-(PF6)) and [(F8-TPP)FeIII(PF6)] (4). Complex 2-(PF6) crystallizes in the orthorhombic space group Iba2 with a = 17.2269(5) Å, b = 17.3143(4) Å, and c = 14.4971(4) Å, Z = 8, complex (5-(Sb/P)F6)1.5(ClO4)0.5 was obtained in the orthorhombic space group P222 with a = 17.9541(2) Å, b = 20.5359(1) Å, and c = 21.2023(2) Å, Z = 4, and 6-(PF6)3 crystallized in the monoclinic space group P21/c with a = 15.318(4) Å, b = 33.921(2) Å, and c = 19.649(6) Å, β = 109.69(2)°, and Z = 4. Compound 5 possesses a low-spin iron(III) center, bridged via cyanide to copper. The iron-cyanide vector deviates slightly from linearity (174.6(5)°). The copper(II) ion is five-coordinated by the TMPA N-donor atoms and the cyanide carbon atom. The Cu(TMPA) moiety is bent with an angle of 163.8(5)° around the cyanide-copper vector. Compound 6 possesses a low-spin iron(III) atom axially coordinated by two cyanide ligands capped on either side by trigonally coordinated [Cu(TMPA)] moieties. The [Cu(1)(TMPA)] unit is twisted somewhat (∠Cu1-N≡C = 168°), whereas the [Cu(2)(TMPA)] unit is coordinated in a nearly linear fashion with respect to the cyanide-iron vector (∠Cu2-N≡C4 = 175°). 1H and 2H NMR spectroscopy on 5 and 6 confirmed the low-spin nature of these iron complexes (pyrrole resonance found at -11.1 and -8 ppm, respectively). The NMR data as well as observed solution magnetic moment (μB = 2.7 for 5; μB = 3.4 for 6) suggest ferromagnetic coupling between the paramagnetic metal ions. This gives rise to an enhancement of the electronic relaxation rate for Cu(II) in both 5 and 6 allowing for the observation of the sharp and downfield shifted TMPA ligand proton signals.
AB - A range of small molecules, such as cyanide, are known to bind and/or inhibit the active site of the heme-copper oxidase enzymes. As such, model studies are aimed at elucidating ligand binding modes and their subsequent impact on spectroscopic properties of derived complexes. We describe here the isolation and characterization of two compounds containing the Fe-CN-Cu moiety, [(py)(F8-TPP)FeIII-CN-CuII(TMPA)]2+ (5) and [(F8-TPP)-FeIII-(CN)2-{Cu II(TMPA)}2]3+ (6) [py = pyridine, TMPA = tris(2-pyridylmethyl)amine, and (F8-TPP) = tetrakis-(2,6-difluorophenyl)porphyrinate(2-)]. [CuII(TMPA)(CH3CN)](ClO4)2 and [(py)(F8-TPP)FeIII(CN)] (3) react to yield 5, while 6 is formed by combination of [CuII(TMPA)(CN)]PF6 (2-(PF6)) and [(F8-TPP)FeIII(PF6)] (4). Complex 2-(PF6) crystallizes in the orthorhombic space group Iba2 with a = 17.2269(5) Å, b = 17.3143(4) Å, and c = 14.4971(4) Å, Z = 8, complex (5-(Sb/P)F6)1.5(ClO4)0.5 was obtained in the orthorhombic space group P222 with a = 17.9541(2) Å, b = 20.5359(1) Å, and c = 21.2023(2) Å, Z = 4, and 6-(PF6)3 crystallized in the monoclinic space group P21/c with a = 15.318(4) Å, b = 33.921(2) Å, and c = 19.649(6) Å, β = 109.69(2)°, and Z = 4. Compound 5 possesses a low-spin iron(III) center, bridged via cyanide to copper. The iron-cyanide vector deviates slightly from linearity (174.6(5)°). The copper(II) ion is five-coordinated by the TMPA N-donor atoms and the cyanide carbon atom. The Cu(TMPA) moiety is bent with an angle of 163.8(5)° around the cyanide-copper vector. Compound 6 possesses a low-spin iron(III) atom axially coordinated by two cyanide ligands capped on either side by trigonally coordinated [Cu(TMPA)] moieties. The [Cu(1)(TMPA)] unit is twisted somewhat (∠Cu1-N≡C = 168°), whereas the [Cu(2)(TMPA)] unit is coordinated in a nearly linear fashion with respect to the cyanide-iron vector (∠Cu2-N≡C4 = 175°). 1H and 2H NMR spectroscopy on 5 and 6 confirmed the low-spin nature of these iron complexes (pyrrole resonance found at -11.1 and -8 ppm, respectively). The NMR data as well as observed solution magnetic moment (μB = 2.7 for 5; μB = 3.4 for 6) suggest ferromagnetic coupling between the paramagnetic metal ions. This gives rise to an enhancement of the electronic relaxation rate for Cu(II) in both 5 and 6 allowing for the observation of the sharp and downfield shifted TMPA ligand proton signals.
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U2 - 10.1021/ic981091s
DO - 10.1021/ic981091s
M3 - Article
AN - SCOPUS:0000309422
SN - 0020-1669
VL - 38
SP - 848
EP - 858
JO - Inorganic Chemistry
JF - Inorganic Chemistry
IS - 5
ER -