N-Substituted pyridazines as building blocks in novel supramolecular architectures

Abstract

A series of mono, 1,4-di and 1,3,5-tri 4-substituted 3,6-di(2-pyridyl)pyridazines were analyzed to evaluate the substituent and steric effects in the crystal packing.Renewed interest in pyridazine chemistry arises from the potential that they have shown in the formation of polynuclear coordination assemblies with diverse topologies including [2 Â 2] grids, 1 metallocryptand cages 2 and helices.3 One of the best studied compounds in this class is 3,6-di(2-pyridyl)pyridazine and its derivatives.4b The N-atoms present multiple coordination sites and their attachments to a variety of metal centres including Cu(I), Ni(II) and Ag(I) facilitate spectroscopic investigation of the resulting photophysical, magnetic and electrochemical properties of any emerging complex array. 5Sterically demanding substituents on the pyridazine ring can force the neighbouring aromatic rings to twist away from the pyridazine ring plane, thus influencing the entire topological and coordination environment. 6 Consequently, selective substitution onto the pyridazine ring offers a mechanism for the manipulation and control of the three-dimensional nature of the assembly.Building on our growing interest in N-rich polyaromatic hydrocarbons, we have generated three aromatically 4-substituted 3,6-di(2-pyridyl)pyridazines 1, 2 and 3 (Scheme 1). ‡ These compounds were synthesized by the inverse electron demand Diels-Alder reaction between 3,6-di(2-pyridyl)-1,2,4,5-tetrazine and the corresponding alkynes.10 There is a correlation between the number of ethynyl units and the temperature employed for the reaction as represented in Scheme 2 (better yields were obtained for the less reactive di-and Scheme 1 The chemical structures of the molecules.

Incorporation of pyridazine rings in the structure of functionalized π-conjugated materials

“…95 Varughese et al have studied a series of mono-1,4-di and 1,3,5-tri-4-substituted 3,6-di(2-pyridyl)pyridazines to evaluate the substituent and steric effects in the crystal packing (Scheme 41). 96 The three-dimensional architecture of the resulting assemblies was dependant of the substitution and the recognition pattern. The one-dimensional coordination polymer 207 exhibits as outstanding feature the rare structure of a meso-helix (Fig.…”

A dinuclear extension to constrained heteroleptic Cu(i) systems

“…A synthetic protocol which can be extended to multiple systems is very attractive and new aromatic ligands generated by Diels-Alder cycloaddition have come to the fore in Ru(II) chemistry. [7][8][9][10] One development in copper chemistry has been the inclusion of stabilizing phosphine ligands, offering a significant improvement on the photophysical properties. McMillin and co-workers have demonstrated that bulky bidentate phosphines (such as POP = bis [2-(biphenylphosphino)phenyl]ether) inhibit the formation of quenching exciplexes, providing unusually long emission lifetimes and rather good quantum yields, typically in the green spectral window.…”

Pyridazines in Crystal Engineering. A Systematic Evaluation of the Role of Isomerism and Steric Factors in Determining Crystal Packing and Nano/Microcrystal Morphologies

“…The 2-pyridyl moieties in phenyl-3,6-di(2-pyridyl)pyridazine, 1a , are in a trans,trans -arrangement with respect to the pyridazine heteroatoms and play no role in the hydrogen bond formation . This can be attributed to the orientation of the pyridyl rings toward an unfavorable sterically demanding environment resulting from the phenyl moiety.…”