title: Ion-pair complexes with strong near infrared absorbance: syntheses, crystal structures and spectroscopic properties.
abstract: Three ion-pair complexes, [4-NH(2)-Py](2)[M(mnt)(2)] (4-NH(2)-Py(1+)=4-amino-pyridinium; mnt(2-)=maleonitriledithiolate; M=Pt (1), Pd (2) or Ni (3)), have been synthesized and characterized. In the crystal of 1, the strong H-bonding interaction was found from the protonated N-atom of pyridinium to the CN group of [Pt(mnt)(2)](2-) together with a weak Pt...H interaction between the anion and the cation. The crystals of 2 and 3 are isostructural with very similar lattice parameters and packing structures, which are distinct from the crystal of 1. Two kinds of strong H-bonding interactions are observed in the crystals of 2 and 3 between the CN groups of [M(mnt)(2)](2-) anion and the protonated N-atom of 4-NH(2)-Py(1+) cation as well as the CN groups of [M(mnt)(2)](2-) anion and the amino group of 4-NH(2)-Py(1+) cation. Complex 1 shows an intense near-IR absorbance in acetonitrile and solid state, such an absorption band is probably assigned to IPCT transition as well as a trace amount of [Pt(mnt)(2)](1-) species; complex 3 possesses a weak near-IR absorption band which can be attributed to the mixture of d-d transition in [Ni(mnt)(2)](2-) and IPCT transition as well as a trace amount of [Ni(mnt)(2)](1-) species.
authors.affiliation: Department of Applied Chemistry, College of Science, Nanjing University of Technology, Nanjing, PR China.
authors.forename: Wen-Bo
authors.initials: WB
authors.lastname: Pei
authors.forename: Jian-Sheng
authors.initials: JS
authors.lastname: Wu
authors.forename: Jian-Lan
authors.initials: JL
authors.lastname: Liu
authors.forename: Xiao-Ming
authors.initials: XM
authors.lastname: Ren
authors.forename: Lin-Jiang
authors.initials: LJ
authors.lastname: Shen
mesh_terms: D003460:Crystallization; D018360:Crystallography, X-Ray; D006860:Hydrogen Bonding; D007477:Ions / Q000737:chemistry*; D008958:Models, Molecular; D008969:Molecular Sequence Data; D015394:Molecular Structure; D009532:Nickel / Q000737:chemistry; D010165:Palladium / Q000737:chemistry; D010984:Platinum / Q000737:chemistry; D011726:Pyridinium Compounds / Q000737:chemistry*; D013057:Spectrum Analysis / Q000379:methods*; D013438:Sulfhydryl Compounds / Q000737:chemistry
chemical_list: D007477:Ions; D011726:Pyridinium Compounds; D013438:Sulfhydryl Compounds; C459462:maleinitriledithiolate; D010984:Platinum; D010165:Palladium; D009532:Nickel