Noncovalent interactions of Cu+ with N-donor ligands (pyridine, 4,4-dipyridyl, 2,2-dipyridyl, and 1,10-phenanthroline): collision-induced dissociation and theoretical studies.
Collision-induced dissociation of complexes of Cu+ bound to a variety of N-donor ligands (N-L) with Xe is studied using guided ion beam tandem mass spectrometry. The N-L ligands examined include pyridine, 4,4-dipyridyl, 2,2-dipyridyl, and 1,10-phenanthroline. In all cases, the primary and lowest-energy dissociation channel observed corresponds to the endothermic loss of a single intact N-L ligand. Sequential dissociation of additional N-L ligands is observed at elevated energies for the pyridine and 4,4-dipyridyl complexes containing more than one ligand. Ligand exchange processes to produce Cu+Xe are also observed as minor reaction pathways in several systems. The primary cross section thresholds are interpreted to yield 0 and 298 K bond dissociation energies (BDEs) after accounting for the effects of multiple ion-neutral collisions, the kinetic and internal energy distributions of the reactants, and dissociation lifetimes. Density functional theory calculations at the B3LYP/6-31G* level are performed to obtain model structures, vibrational frequencies, and rotational constants for the neutral N-L ligands and the Cu+(N-L)x complexes. The relative stabilities of the various conformations of these N-L ligands and Cu+(N-L)x complexes as well as theoretical BDEs are determined from single point energy calculations at the B3LYP/6-311+G(2d,2p) level of theory using B3LYP/6-31G* optimized geometries. Excellent agreement between theory and experiment is observed for all complexes containing one or two N-L ligands, while theory systematically underestimates the strength of binding for complexes containing more than two N-L ligands. The ground-state structures of these complexes and the trends in the sequential BDEs are explained in terms of stabilization gained from sd-hybridization and repulsive ligand-ligand interactions. The nature of the binding interactions in the Cu+(N-L)x complexes are examined via natural bond orbital analyses.
Rannulu
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NS
Department of Chemistry, Wayne State University, Detroit, MI 48202, USA.
Rodgers
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MT
D015082:2,2'-Dipyridyl / Q000737:chemistry; D002413:Cations, Divalent; D003300:Copper / Q000737:chemistry*; D007700:Kinetics; D008024:Ligands; D008958:Models, Molecular; D009584:Nitrogen / Q000737:chemistry*; D010618:Phenanthrolines / Q000737:chemistry; D011725:Pyridines / Q000737:chemistry; D053719:Tandem Mass Spectrometry; D013816:Thermodynamics; D014978:Xenon / Q000737:chemistry*
D002413:Cations, Divalent; D008024:Ligands; D010618:Phenanthrolines; D011725:Pyridines; D014978:Xenon; D015082:2,2'-Dipyridyl; D003300:Copper; D009584:Nitrogen; C023666:pyridine