Dinuclear metal carboxylates are unique metal complexes, having a lantern-type (paddlewheel-type) dinuclear core (Fig. 1). We have engaged in coordination chemistry of metal carboxylates, paying attention to their utility as building blocks to construct metalassembled complexes. Among them, copper(II) carboxylates and ruthenium(II,III) carboxylates are few examples showing paramagnetic properties contrary to diamagnetism of most metal carboxylates. The former carboxylates have no metal-metal bonding in their dinuclear cluster and show a superexchange interaction between the two unpaired electrons, whereas the latter carboxylates have three unpaired electrons in the metal-metal bond orbitals with large zero-field splitting. We have prepared many metal-assembled complexes from one-dimensional chain compounds to oligonuclear metal species by application of some bidentate linking lignads L to dinuclear metal carboxylates [1,2]. We found that magnetic interaction between the dinuclear units is antiferromagnetic in most cases and the strength of the interaction depends on the linking ligand L. Ferromagnetic and ferrimagnetic interactions were also observed for some ruthenium systems. Herein, we report on the structures and magnetic properties of these systems. The mesomorphic properties [3] as well as the magnetic properties [4] will be discussed in relation to the crystal structures.figureFig. 1. Dinuclear metal carboxylates.