Formylbiliverdin and related chlorophyll-derived molecules are possible products of heme catabolism and other biologically important oxidative processes and are likely to be initially formed as metal complexes. To explore the properties of the formylbiliverdin moiety bound to transition metal ions, complexes of octaethylformylbiliverdin (H2OEFB) with Cu(II), Ni(II), and Co(II) have been prepared, since attempts to prepare an iron complex have produced only an unstable material. Transmetalation of MgII(OEFB), made by photooxidation of MgII(octaethyl-porphyrin), with a metal(II) acetate yields the low-spin complexes:  CuII(OEFB), NiII(OEFB), and CoII(OEFB). Single-crystal X-ray diffraction of CuII(OEFB) reveals that it consists of a four-coordinate copper(II) center which is bound to the four nitrogen atoms in distorted planar coordination. The tetrapyrrole ligand has a helical geometry. The structure of the solid is complicated by the existence of three molecules in the asymmetric unit and C−H···O hydrogen bonding between pairs of these in the tab/slot arrangement seen in complexes of octaethylbiliverdin. Both CuII(OEFB) and CoII(OEFB) can be converted to the verdoheme analogues, [CuII(OEOP)]+ and [CoII(OEOP)]+, where OEOP is the anion of octaethyl-5-oxaporphyrin, by the addition of hydrogen peroxide. Additionally, [CuII(OEOP)]+ can be produced by heating a toluene solution CuII(OEFB) in the presence of trifluoroacetic acid under dioxygen. Carbon monoxide is produced when CuII(OEFB) is converted to [CuII(OEOP)]+ by either method. [CuII(OEOP)](PF6) has been characterized by single-crystal X-ray diffraction which shows that the cation has a planar, porphyrin-like structure. The room-temperature EPR spectrum of this complex shows that the copper is four-coordinate with four nitrogen based ligands, but frozen solutions of [CuII(OEOP)]+ show a triplet EPR spectrum indicative of a dimeric species much like that in the X-ray crystal structure. The 1H NMR spectrum of diamagnetic NiII(OEFB) has been shown to be consistent with the helical structure through the use of lanthanide and chiral lanthanide shift reagents. The EPR spectra of CoII(OEFB) show that it forms a low-spin adduct with pyridine and that this adduct acts as a reversible dioxygen carrier. The geometric and electronic structural properties of these complexes of formylbiliverdin are compared to those of analogous compounds of biliverdin and of porphyrins.

Crystals of (Aul)2Ip-bis(diphenylphosphino)hexanel f o r m polymeric chains (through Au-Au contacts), which are interwoven t o produce discrete layers that lie between cleavage planes of the crystal.The production of extended solid state structures (with the potential for novel optical, electronic, magnetic and mechanical properties) from small molecular or ionic components represents a new challenge to chemical synthesis. Self-assembly techniques are an effective means to take advantage of weak interactions between molecules to create a more complex superstructure. Intermolecular interactions that have been used to produce such superstructures include hydrogen bonding,' weak metal ion coordination,2 and shaped van der Waals forces.3 Here, we describe a new woven layered structure, which uses the attractive interaction between two gold(1) ions to connect the molecular components. This attractive interaction has been estimated to be comparable in energy to a hydrogen bond4 and to result in contact between two gold(1) ions of less than 3.5 A . 5A survey of the Cambridge Crystallographic Data Base6 augmented with data from this laboratory indicates that AuL AuI contacts are present in 16% of the 25 examples of compounds of the type (R3P)AuX where X is a halide ligand. However, when a diphosphine ligand is used, the occurrence of these AuLAuI contacts increases. Of the 23 examples, 26% display intramolecular interactions and a remarkable 6 1 % display intermolecular interactions. Those in the latter category generally form chains, 1.7 The formation of discrete dimers, 2, is less common with only two examples found.8 The polymeric compounds, 1, can have the chains running parallel or crisscrossing one another. However, with (AuI)z(pdpph) we have observed the formation of an unprecedented woven layered structure the complexity of which exceeds that seen in other solids of type 1.Colourless crystals of (AuCl)z(p-dpph) [dpph is bis(diphenylphosphino)hexane] were prepared by mixing (Me2S)-AuCl with dpph in CHzClz and precipitation of the complex by the addition of diethyl ether. These were subsequently converted into (AuI)z(p-dpph) by treatment with tri(butyl)(prop-y1)ammonium iodide in MeOH. The results of X-ray diffraction studies of (AuCl)z(p-dpph), crystallized from CHZClJdiethyl ether, and (AuI)z(p-dpph), crystallized from CHZClJmethanol, are shown in Fig. 1-3.t Fig. 1 shows the basic molecular structure of the individual dinuclear complexes. In each case the hexane chain adopts a staggered conformation and is fully elongated. The P-Au-X groups are nearly linear. While both P-Au-Cl groups in (AuCl)Z(p-dpph) jut out almost perpendicularly to the line of methylene groups, only one of the P-Au-I groups in (AuI)z(p-dpph) adopts a similar orientation. The other is positioned so that it extends approximately in the direction of the methylene chain. The intermolecular interactions in the two compounds differ markedly. In (Ad)&dpph), Au(1) in one molecule interacts with Au(2) in the next.

A systematic study is reported of the effects of weak attractive AuI···AuI interactions on the solid state structures of six crystalline polymers from molecules of the type XAuPnPAuX, where X is iodide or chloride and PnP is Ph2P(CH2) n PPh2 with n = 4−8. Crystallographic data for the six molecules IAuP4PAuI, IAuP5PAuI, IAuP6PAuI, ClAuP7PAuCl·CH3OH, IAuP8PAuI·CH2Cl2, and ClAuP8PAuCl·CH2Cl2 are presented. In each case, the complexes appear to be symmetrical monomeric species in solution, as shown by the simple, single-line 31P NMR spectra. However, they form linear chains in the solid state with individual molecules connected through close Au···Au contacts at each end of the molecule. These solids are analyzed in terms of the structures of individual molecules, geometries of Au···Au interactions, methods of chain propagation, and relative orientations of individual chains. Only two types of propagation (pure translation and translation along a glide plane) of individual molecules are observed. The chains arrange themselves in three motifs:  strands that run parallel, layers of strands that criss-cross, and layers with an interwoven strand structure.

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Two very different molecular shapes are formed using the ligand 1,3,5-tris(diphenylphosphino)benzene (L); polymeric chains form through Au-Au contacts in the crystals of [(CIAU)~L], while the metallocyclophane [(PtC&L2] self assembles from five components when L and [PtC12(cod)] are combined in a 2 : 3 molecular ratio.

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In the presence of dioxygen, four cobalt complexes of linear tetrapyrroles, Co(OEB) (OEB is the trianion of octaethylbiliverdin), [CoII(OEBOx)]I3 (OEBOx is the monoanion of the oxidized form of octaethylbiliverdin), CoII(OEFB) (OEFB is the octaethylformylbiliverdin dianion), and CoII(OEBOMe) (OEBOMe is the dianion of octaethylmethoxybiliverdin) form the bischelate cobalt(II) complex of the anionic dipyrrole, tetraethylpropentdyopent anion, CoII(TEPD)2. Both carbon monoxide and carbon dioxide are formed when CoII(TEPD)2 is produced by the thermal reactions between CoII(OEFB) or Co(OEB) and O2. Three different crystal morphologies of CoII(TEPD)2 have been analyzed by single-crystal X-ray diffraction. In each case the cobalt atom is coordinated by four nitrogen atoms of the two propentdyopent ligands in a pseudotetrahedral fashion. In each morphology, a common tab/slot intermolecular C−H···O hydrogen bond interaction that involves the methine C−H unit and two adjacent C−H units of the flanking ethyl groups and the lactam oxygen atom is found. These interactions connect pairs of molecules into extended chains. CoII(TEPD)2 has been characterized spectroscopically (UV−vis and NMR) and electrochemically.

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