In this paper, we describe the synthesis and study of a series of heme/non-heme Fe-O-Fe' complexes supported by a porphyrin and the tripodal nitrogen ligand TMPA [TMPA = tris(2-pyridylmethyl)amine]. The complete synthesis of [((6)L)Fe-O-Fe(X)](+) (1) (X = OMe(-) or Cl(-), 69:31 ratio), where (6)L is the dianion of 5-(o-O-[(N,N-bis(2-pyridylmethyl)-2-(6-methoxyl)pyridinemethanamine)phenyl]-10,15,20-tris(2,6-difluorophenyl)porphine, is reported. The crystal structure for 1.PF(6) reveals an intramolecular heme/non-heme diferric complex bridged by an Fe-O-Fe' moiety; 90 degree angle (Fe-O-Fe') = 166.7(3) degrees, and d(Fe.Fe') = 3.556 A. Crystal data for C(70)H(57)ClF(12)Fe(2)N(8)O(3)P (1.PF(6)): triclinic, Ponemacr;, a = 13.185(3) A, b = 14.590 (3) A, c = 16.885(4) A, alpha = 104.219(4) degrees, beta = 91.572(4) degrees, gamma = 107.907(4) degrees, V = 2977.3(11) A(3), Z = 2, T = 150(2) K. Complex 1 (where X = Cl(-)) is further characterized by UV-vis (lambda(max) = 328, 416 (Soret), 569 nm), (1)H NMR (delta 27-24 [TMPA -CH(2)-], 16.1 [pyrrole-H], 15.2-10.5 [PY-3H, PY-5H], 7.9-7.2 [m- and p-phenyl-H], 6.9-5.8 [PY-4H] ppm), resonance Raman (nu(as)(Fe-O-Fe') 844 cm(-)(1)), and Mössbauer (delta(Fe) = 0.47, 0.41 mm/s; deltaE(A) = 1.59, 0.55 mm/s; 80 K) spectroscopies, MALDI-TOF mass spectrometry (m/z 1202), and SQUID susceptometry (J = - 114.82 cm(-)(1), S = 0). We have also synthesized a series of 3-, 4-, and 5-methyl-substituted as well as selectively deuterated TMPA(Fe') complexes and condensed these with the hydroxo complex (F(8))FeOH or (F(8)-d(8))FeOH to yield "untethered" Fe-O-Fe' analogues. Along with selective deuteration of the methylene hydrogens in TMPA, complete (1)H NMR spectroscopic assignments for 1 have been accomplished. The magnetic properties of several of the untethered complexes and a comparison to those of 1 are also presented. Complex 1 and related species represent good structural and spectroscopic models for the heme/non-heme diiron active site in the enzyme nitric oxide reductase.

Metallation (FeC12 followed by aeration) of 5L, possessing a tris(2-pyridylmethy1)amine (tmpa) moiety tethered to a synthetic porphyrin, leads to an 0x0-bridged haednon-haem iron complex [(5L)Fe~~LO-Fe~~I(Cl)] + 1; its structure and properties compare closely with an analogue assembled via an acid-base synthesis, [(Fg-tpp)FeIII(tmpaInterest in 0x0-bridged homo-or hetero-dinuclear metal complexes derives from the versatility and bonding of the 0 2ligand, applications to catalysis, magnetic exchange and electron-transfer phenomena, modelling metalloprotein active sites, and synthetic considerations.l Here, we report the construction and preliminary characterization of members of a new class of 0x0-bridged diiron complexes,2 containing haem and non-haem iron mixed environments.Ligand 5L (Scheme 1) allows generation of dinuclear complexes where intramolecular reactions of metal ions in differing environments are favoured; it was prepared by condensation of a pyridyl 5-chloromethyl derivative of tmpa3 with a monophenol-derivatized tetraarylporphyrin. Iron insertion was accomplished by refluxing with an excess of FeC12 in dmf, exposure to 02, and precipitation of the product by the addition of brine. Counter-ion exchange using NaC104 followed by column chromatography affords [(5L)FerrLO-FeIII(C1)]-(C104) (lClO,).t An X-ray crystal structure analysis (Fig. l)$ reveals the y-0x0 group which connects the haem and non-haem FelI1 atoms., The porphyrinate-iron(II1) coordination closely b r 5L

Received December 29, 1994®The copper complexes of bis [2-(3,5-dimethyl-l-pyrazolyl)ethyl]amine (1) and its benzylated derivative (2) have been studied as single crystals by X-ray crystallography and as powders and solutions by a variety of techniques.[Cu(l)*2 N Û 3] (C 14H 25CUN7O 7 including 1 H 2O, 3) crystallized in the monoclinic space group Pc (No. 7) with a bis(pyrazole) complexes, in particular for complex 6 , are explained by the fact that the Cu(II) complexes have the correct ligand geometry for the stabilization of Cu(I). duction e elucidation of the mechanisms2-4 by which the dicopper loprotein hemocyanin5 binds dioxygen continues to be a c of great interest.6-8 Model compounds mimicking the n of hemocyanin and related metalloproteins have been ed and synthesized by several groups.9-11 Karlin and orkers have shown that Cu(I) bis(pyridine) complexes are tive dioxygen binders.12,13 Sorrell and co-workers on the uthor to whom correspondence should be addressed, sent address: Department of Chemistry. other hand have presented evidence that the related copper(I) bis(pyrazole) complexes do not bind dioxygen. 14 More detailed insight in the factors regulating the properties of these types of complexes is therefore required.Recently, we reported on the reduction of Cu(II) bis(pyrazole) crown ether complexes in alcoholic solutions.I:> The observed rapid reduction of the Cu(II) complexes, and the remarkable stability of the Cu(I) species, even in the presence of dioxygen, prompted us to investigate this system in detail. In particular we were interested to elucidate the factors that control the geometry, electrochemical behavior, and reactivity of our Cu-(II) bis(pyrazole) complexes.Central in this study are the ligands bis[2-(3,5-dimethyl-lpyrazolyl)ethyl]amine (1) and the benzylated derivative 2 (Chart 1). These two ligands are treated with Cu(N0 3 )2*3 H2 0 and Cu-(10) Kitajima, N.; Fujisawa, K