Co-crystallization of coordination compounds through second-coordination sphere interactions

Abstract

The mononuclear complexes belonging to the [M(valXn)]^0/+ family [H₂valXn are bicompartmental ligands derived from o-vanillin and 1,2- or 1,3-diamines; M = Ni(II), Cu(II), Au(III)] can efficiently act as receptors towards various hydrogen bond donors. The co-crystallization processes between [Ni(valXn)] complexes and ammonium salts (NH₄Z, Z⁻ = ClO₄⁻; PF₆⁻; C₆H₅NH₃ClO₄) led to different supramolecular arrangements in the crystals depending on the host : guest molar ratio used in reactions. For a 2 : 1 stoichiometry, supramolecular dimers were obtained in the crystals: 2[Ni(valen)]·NH₄Z (Z⁻ = ClO₄⁻, 1a; Z⁻ = PF₆⁻, 1b), 2[Ni(valphen)]·NH₄ClO₄·CH₃OH 1c, 2[Ni(valmen)]·C₆H₅NH₃ClO₄3, while for a 1 : 1 stoichiometry a supercomplex with a quadruple deck architecture resulted: 4[Ni(valen)]·3NH₄ClO₄2. The co-crystallization of the Reinecke salt with mononuclear complexes from the [M(valXn)] family affords the following crystals: [Ni(valen)]₂·NH₄[Cr(NCS)₄(NH₃)₂]·CH₃OH 4, [Ni(valdmpn)]₂·NH₄[Cr(NCS)₄(NH₃)₂]·2H₂O 5, and [Cu(valpn)]·NH₄[Cr(NCS)₄(NH₃)₂]·CH₃CN 6, in which the [M(valXn)] complexes interact with the ammonium ions and ammonia ligands, resulting in supramolecular chains. The composition and the topology of the supramolecular chain can be changed by replacing the ammonium ion from the Reinecke salt with a cationic receptor, [Au(valpn)]⁺ : [Au(valpn)][Cr(NCS)₄(NH₃)₂] 7.