Designed Topology and Site-Selective Metal Composition in Tetranuclear [MM′⋅⋅⋅M′M] Linear Complexes

• Published in: Chemistry : a European journal Vol. 15; no. 42; pp. 11235 - 11243
• Main Authors: Barrios, Leoní A., Aguilà, David, Roubeau, Olivier, Gamez, Patrick, Ribas-Ariño, Jordi, Teat, Simon J., Aromí, Guillem
• Format: Journal Article
• Language: English
• Published: Weinheim WILEY-VCH Verlag 26.10.2009; WILEY‐VCH Verlag
• Subjects: heterometallic complexes; ligand design; magnetic properties; quantum chemistry
• ISSN: 0947-6539; 1521-3765
• DOI: 10.1002/chem.200901534

The ligand 1,3‐bis[3‐oxo‐3‐(2‐hydroxyphenyl)propionyl]benzene (H4L), designed to align transition metals into tetranuclear linear molecules, reacts with MII salts (M=Ni, Co, Cu) to yield complexes with the expected [MM⋅⋅⋅MM] topology. The novel complexes [Co4L2(py)6] (2; py=pyridine) and [Na(py)2][Cu4L2(py)4](ClO4) (3) have been crystallographically characterised. The metal sites in complexes 2 and 3, together with previously characterised [Ni4L2(py)6] (1), favour different coordination geometries. These have been exploited for the deliberate synthesis of the heterometallic complex [Cu2Ni2L2(py)6] (4). Complexes 1, 2, 3 and 4 exhibit antiferromagnetic interactions between pairs of metals within each cluster, leading to S=0 spin ground states, except for the latter cluster, which features two quasi‐independent S=1/2 moieties within the molecule. Complex 4 gathers the structural and physical conditions, thus allowing it to be considered as prototype of a two‐qbit quantum gate. Everyone take their seats! Designed nuclearity, topology and site distribution of four paramagnetic metals within molecular strings has been achieved through use of a bis‐β‐diketophenol ligand (see image). Three homometallic species exhibit linear arrays of two semi‐independent dimers, whereas crystal‐field effects allow for the synthesis of the heterometallic analogue [CuNi⋅⋅⋅NiCu].