Determination of the "Privileged Structure" of 8‐Hydroxyquinoline. Issue 16 (7th July 2021)

• Record Type: Journal Article
• Authors: McNaughton, Donald; Wachsmuth, Dennis; Kraus, Peter; Herbers, Sven; Wang, Juan; Grabow, Jens‐Uwe
• Is Part Of: Chemphyschem. Volume 22:Issue 16(2021)
• Page Start: 1692
• Page End: 1697
• Publication Date: 2021-07-07
• Subjects: 8-hydroxyquinoline -- density functional calculations -- microwave spectroscopy -- molecular structure -- privileged structure; Chemistry, Physical and theoretical -- Periodicals; 541.05
• DOI: 10.1002/cphc.202100384
• Languages: English
• ISSNs: 1439-4235

Abstract

Abstract: An accurate semi‐experimental equilibrium structure of 8‐hydroxyquinoline (8‐HQ) has been determined combining experiment and theory. The cm‐wave rotational spectrum of 8‐HQ was recorded in a pulsed supersonic jet using broadband dual‐path reflection and narrowband Fabry‐Perot‐type resonator Fourier‐transform microwave spectrometers. Accurate rotational and quartic centrifugal distortion constants and 14 N quadrupole coupling constants are determined. Rotational constants of all 13 C, 18 O and 15 N singly substituted isotopologues in natural abundance and those of a chemically synthesized OD isotopologue were used to obtain geometric parameters for all the heavy atoms and the hydroxyl hydrogen from a number of structure determination models. Theoretical approaches allowed for the determination of a semi‐experimental equilibrium structure, r e SE in which computed rovibrational and electronic corrections were utilized to convert vibrational ground state constants into equilibrium constants. Despite the molecule having only a horizontal plane of symmetry and possessing 11 individual heavy atoms, microwave spectroscopy has allowed for a reliable and accurate structure determination. A mass dependent, r m 2 structure was determined and proved to be equally reliable by comparison with the B3LYP‐D3(BJ)/aVTZ equilibrium structure. Abstract : A good combination ! The pharmacologically important framework structure of 8‐hydroxyquinoline is determined through a combination of microwave spectroscopy and quantum mechanical calculations. For this large molecule, the mass dependent structure that minimizes errors due to isotopologue vibrational differences is the most satisfactory structure.