Studies on spin-equilibrium iron(III) complexes. I: Syntheses and magnetic properties of a new family of spin cross-over iron(III) complexes with a unidentate ligand over a wide range of the spectrochemical series and a quinquedentate ligand derived from salicylaldehyde and Di(3-aminopropyl)amine. X-ray crystal structure of [4-azaheptamethylene-1,7-bis(salicylideneiminato)](4-methylpyridine)iron(III) tetraphenylborate