Stéphane A. Baudron

Dipyrrin based homo- and hetero-metallic infinite architectures

The use of α,β-unsubstituted dipyrrins, dpm, for the elaboration of infinite architectures in crystalline form based on coordination as well as hydrogen bonding interactions is reviewed. These ligands can be readily functionalized and derivatives bearing either a peripheral hydrogen bond donor/acceptor group or a secondary coordinating group have been developed. In the first case, the complexes incorporating these dpms self-assemble via hydrogen bonding leading to extended architectures. In the second case, the coordinating complexes, or metallatectons, can self-assemble to form homonuclear networks such as in a series of (acac)Cu(dpm) complexes. Upon association of the metallatectons with a second metal centre, heterometallic architectures are formed. These MOFs are constructed by coordination as well as Ag-π interactions depending on the nature of the peripheral coordinating group and the coordination geometry of the metallatecton.

Assembly of heteroleptic copper complexes with silver salts: from discrete trinuclear complexes to infinite networks.

The use of heteroleptic copper complexes functionalized with two differentiated coordinating groups for the elaboration of heterometallic extended networks is presented. Two novel 5-phenyl-dipyrrin (dpm) ligands appended with an imidazole or a pyrazole function, dpm-imid and dpm-pz, have been prepared and used as ligands for the synthesis of a series of heteroleptic (acacR)Cu(dpm) complexes (acacH = acetylacetonate; acacCN = 3-cyanoacetylacetonate). The X-ray crystal structures of these complexes revealed that, albeit no particular association mode is observed for the acac capping ligand, one-dimensional networks are formed with the acacCN capping ligand. Whereas the imidazole peripheral ligand is coordinated to the copper center of a neighboring complex in the structure of (acacCN)Cu(dpm-imid), such an interaction is absent for the pyrazole appended derivative, (acacCN)Cu(dpm-pz), leading to an association mode involving the peripheral nitrile group of the acacCN ligand. Upon reaction of the imidazole functionalized complexes, (acac)Cu(dpm-imid) and (acacCN)Cu(dpm-imid), with silver salts, trinuclear species, {[(acacR)Cu(dpm-imid)](2)Ag}(+), are formed as a result of the coordination of the azole nitrogen atom of two copper complexes to the silver ion. As expected, in the case of (acac)Cu(dpm-imid), these species do not self-assemble into an extended network owing to the absence of a peripheral coordinating group. However, for the (acacCN)Cu(dpm-imid) complex, the trinuclear species are equipped with peripheral nitrile groups, thus allowing the binding of metal centers. Consequently, these species self-assemble into one-dimensional polymers with association modes varying with the nature of the anion present in the silver salt.

Beyond classical coordination: silver–π interactions in metal dipyrrin complexes

Homo- and hetero-leptic Zn and Cu complexes of dipyrrin type ligands bearing mono- and di-cyanophenyl groups when combined with silver cations lead to the formation of Ag(I)-C=C double bond interactions unprecedented in the crystalline phase.

Many faces of dipyrrins: from hydrogen-bonded networks to homo- and heteronuclear metallamacrocycles.

The amphoteric 5-(4-cyanophenyl)dipyrrin ligand, offering three distinct states, i.e., cationic, neutral, and anionic, has been exploited for the formation of a 1-D hydrogen-bonded network in its protonated form and both homo- and heterobinuclear metallamacrocycles, in its neutral and deprotonated states, respectively, with a variety of coordination modes.

Heterometallic Architectures Based on the Combination of Heteroleptic Copper and Cobalt Complexes with Silver Salts

A strategy for the formation of heterometallic coordination polymers based on novel copper(II) and cobalt(III) heteroleptic complexes (acacCN)Cu(dpm) and (acacCN)Co(dpm)(2) (acacCN = 3-cyanoacetylacetonate; dpm = dipyrrin) is presented. Using dipyrrins appended with a p- or m-pyridyl group, dpm-4py and dpm-3py, four novel copper and cobalt complexes were prepared and characterized both in solution and in the solid state. These two classes of complexes show different electrochemical properties upon investigation by cyclic voltammetry in CH(2)Cl(2). While the copper complexes show only irreversible reduction processes, the voltammogram of the cobalt species reveals the presence of two quasi-reversible reductions. In the solid state, the copper(II) compounds self-assemble to form one-dimensional architectures upon coordination of the peripheral pyridyl group to the copper center, as characterized by single-crystal X-ray diffraction. Owing to the filled coordination sphere of the octahedral cobalt centers, the (acacCN)Co(dpm-py)(2) compounds crystallize as isolated molecules. Upon reaction with silver salts, these complexes form crystalline heterometallic architectures with different organization and dimensionality, depending on the nature of the metal center and the position of the nitrogen atom in the pyridyl group. The two copper complexes lead to the formation of trinuclear species, {[(acacCN)Cu(dpm-py)](2)Ag}(+), resulting from coordination of the pyridyl groups to the silver cations. However, while meta-functionalized complexes self-assemble into an extended architecture via weak interaction of the peripheral nitrile of the acacCN ligand to the Ag(+) cation, this interaction is not present in the para-functionalized analogue. In both networks based on the Ag(BF(4)) salt, coordination of the tetrafluoroborate anion to the silver center in the rather rare chelate mode is observed. Upon assembly of the cobalt metallatectons with silver salts, two-dimensional (2D) coordination polymers are obtained in crystalline form, resulting, however, from different sets of interactions. Indeed, no coordination of the peripheral nitrile of the acacCN ligand is observed in the network incorporating the m-pyridyl-appended dpm; coordination of the pyridyl groups to the silver center and d(10)-d(10) interactions lead to a 2D architecture. In the case of the para analogue, a 2D honeycomb network is observed owing to coordination of the Ag(I) ion to two pyridyl nitrogen atoms and to one peripheral nitrile group of a acacCN ligand. This latter polymer represents a geometrical hybrid of the networks reported in the literature based on homoleptic Co(dpm-4py)(3) and Cr(acacCN)(3) complexes.

Carboxylic Acid Appended Dipyrrin for the Formation of a Hexanuclear Iridium/Copper Paddlewheel Complex

Reaction of a heteroleptic cyclometalated iridium complex incorporating a carboxylic acid appended dipyrrin with copper acetate leads to the formation of a hexanuclear species with the paddlewheel structure.

Excited state properties and energy transfer within dipyrrin-based binuclear iridium/platinum dyads: the effect of ortho-methylation on the spacer.

Luminescent cyclometalated iridium complexes based on pyridyl appended dipyrrin ligands were prepared and characterized both in the solid state and in solution. The functionalization of the peripheral pyridyl moiety causes dramatic changes on the emission properties of both mono- and hetero- binuclear complexes. A detailed photophysical investigation of the two mononuclear derivatives of the [(Ppy)(2)Ir(dpm-py)] family (Ppy=2-phenylpyridine, dpm-py=5-(4-pyridyl)dipyrrin) was carried out. Introduction of methyl groups at the 3 and 5 positions on the pyridyl unit diminishes the non-radiative rate constant by locking the peripheral pyridyl group orthogonally to the dipyrrinato plane. Thus, they limit the rotational degree of freedom, as well as the charge-transfer character of the excited state. The coordination of these two complexes to a cyclometalated [(dppy)Pt] fragment (dppy=2,6-diphenylpyridine) led to the formation of binuclear species in which the iridium and platinum complexes behave as acceptors and donors, respectively. In these heterobinuclear compounds, the methyl groups do not influence the energy transfer efficiency, which is estimated to be above 90 %. However, they do limit the charge-transfer character of the acceptors excited state, as well as its rotational degree of freedom, thus avoiding the detrimental effect upon the photophysical performance.

Combination of primary amide and dipyrrin for the elaboration of extended architectures built upon both coordination and hydrogen bonding

The 5-(benzamide)dipyrrin, a ditopic tecton bearing two different interaction poles, i.e. a primary amide as H-bond donor and acceptor and a deprotonated dipyrrin unit as a strong chelating group leads in the presence of metal cations (Cu(II), Zn(II..)) or metal complexes ([Cu(II)-acac]+ and [Co(III)-salen]+) to homo- and heteroleptic complexes. The latter behave as metallo-organic tectons and generate in the crystalline phase molecular networks. Whereas the homoleptic Cu complex leads to the formation of a 2-D network, its Zn analogue forms a 1-D ribbon type architecture owing to the presence of capping dioxane molecules. For the heteroleptic complexes, in the case of the Cu-acac, a 1-D network resulting from bridging of H-bonded dimers of dimers by dioxane molecules is observed whereas for the Co-salen, due to the salen ligand offering further hydrogen bonding capabilities, two different solvates with different connectivity patterns have been obtained.

Stepwise construction of grid-type Cu(II)–Cd(II) heterometallic MOFs based on an imidazole-appended dipyrrin ligand

An imidazole-appended dipyrrin ligand yields, upon coordination to Cu(II) cations, a linear metallatecton that self-assembles with Cd(II) salts to afford 2D grid-type MOFs which, upon parallel stacking, lead to porous crystals offering 1D channels.

Luminescent Coordination Polymers Based on Self‐Assembled Cadmium Dipyrrin Complexes

A series of novel Cd(II) complexes based on α,β-unsubstituted dipyrrin ligands (dpm) has been prepared and characterised both in solution and in the solid state. These compounds are of the [Cd(dpm)(2)] type, with the coordination sphere of the metal centre occupied by two dpm chelates. Interestingly, in contrast to what has been reported for the Zn(II) analogues, in the presence of a pyridyl- or imidazolyl-appended dpm ligand, the coordination number of the Cd(II) cation can be increased to six, leading to an octahedral coordination sphere. As a consequence, the formation of 1-, 2-, and 3D coordination polymers by self-assembly is observed. Photophysical investigations of the discrete complexes and self-assembled networks have demonstrated that both types of compounds are luminescent in the solid state.