## Abstract

The rotational spectra of six isotopologues of a complex of ethyne and silver acetylide, C2H2 ... AgCCH, are measured by both chirped-pulse and Fabry-Perot cavity versions of Fourier-transform microwave spectroscopy. The complex is generated through laser ablation of a silver target in the presence of a gas sample containing 1% C2H2, 1% SF6, and 98% Ar undergoing supersonic expansion. Rotational, A(0), B-0, C-0, and centrifugal distortion Delta(J) and Delta(JK) constants are determined for all isotopologues of C2H2 ... AgCCH studied. The geometry is planar, C-2 nu and T-shaped in which the C2H2 sub-unit comprises the bar of the "T" and binds to the metal atom through its pi electrons. In the r(0) geometry, the distance of the Ag atom from the centre of the triple bond in C2H2 is 2.2104(10) angstrom. The r(HC equivalent to CH) parameter representing the bond distance separating the two carbon atoms and the angle, angle(CCH), each defined within the C2H2 sub-unit, are determined to be 1.2200(24) angstrom and 186.0(5)degrees, respectively. This distortion of the linear geometry of C2H2 involves the hydrogen atoms moving away from the silver atom within the complex. The results thus reveal that the geometry of C2H2 changes measurably on coordination to AgCCH. A value of 59(4) Nm(-1) is determined for the intermolecular force constant, k sigma, confirming that the complex is significantly more strongly bound than hydrogen and halogen-bonded analogues. Ab initio calculations of the re geometry at the CCSD(T)(F12*)/ACVTZ level of theory are consistent with the experimental results. The spectra of the (AgCCH)-Ag-107-C-13-C-13 and (AgCCH)-Ag-109-C-13-C-13 isotopologues of free silver acetylide are also measured for the first time allowing the geometry of the AgCCH monomer to be examined in greater detail than previously. (c) 2014 AIP Publishing LLC.

Original language | English |
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Article number | 124310 |

Number of pages | 13 |

Journal | Journal of Chemical Physics |

Volume | 140 |

Issue number | 12 |

DOIs | |

Publication status | Published - 28 Mar 2014 |

## Keywords

- CONSISTENT BASIS-SETS
- CONVERGENT BASIS-SETS
- HYPERFINE CONSTANTS
- MOLECULAR-STRUCTURE
- TRANSITION-METALS
- MICROWAVE SPECTROSCOPY
- WAVE-FUNCTIONS
- CORE-VALENCE
- CENTER-DOT
- COMPLEX