65 th International Symposium on Molecular Spectroscopy June 21, 2010 Lindsay N. Zack Brent J. Harris Matthew P. Bucchino Ming Sun Lucy M Ziurys Department of Chemistry, Department of Astronomy, Steward Observatory, and Arizona Radio Observatory University of Arizona Dennis Clouthier Department of Chemistry, University of Kentucky

65 th International Symposium on Molecular Spectroscopy June 21, 2010  Zn important in many metalloenzymes  Lewis acid, no redox function  LFSE zero, multiple geometries  Hard/soft borderline (S,O,N)  As co-factor or catalyst  ZnOH in carbonic anhydrase II  Transport of CO 2 and pH regulation via CO 2 /HCO 3 -  Zn function is catalytic, ligand exchange  The Zn coordination sphere has received most of the attention but what about the ZnOH unit itself

65 th International Symposium on Molecular Spectroscopy June 21, 2010  Alkali and alkaline earth hydroxides have linear or quasilinear  metals out of the main group are bent HOH LiOHBeOH NaOHMgOHAlOH KOHCaOHScOHTiOHVOHCrOHMnOHFeOHCoOHNiOHCuOHZnOHGaOH RbOHSrOHYOH AgOH InOH CsOHBaOH ScTiVCrMnFeCoNiCuZn OH 33 4A"4A" 5A"5A" 6 A' 7 A' 6 A' 3 A' 2 A' 1 A' 2 A'

65 th International Symposium on Molecular Spectroscopy June 21, 2010  Asymmetric top  Near prolate rotor  a-type transitions (  K a = 0)  Spin rotation splitting from unpaired electron  Approx 190 MHz from ZnOH  Five naturally occurring zinc isotopes  64 Zn (48.6%), 66 Zn (27.9%), 68 Zn (18.8%), 67 Zn (4.1), 70 Zn (0.6%)  Production  H 2 O in Ar carrier gas, DC discharge assisted (250mA, 200V)  Inconsistent production

65 th International Symposium on Molecular Spectroscopy June 21, 2010  D 2 O (2 mT) in Zn vapors and Ar (15mTorr)carrier gas, DC discharge assisted (250mA at 300V) Instrumentation:  Phase-locked Gunn oscillators and Schottky diode multipliers ( GHz)  Broida-type oven  Gaussian beam optics  Reaction chamber: double-pass, water- cooled steel cell containing a Broida- type oven  InSb bolometer detector  Radiation is modulated at 25 kHz and detected at 2f

65 th International Symposium on Molecular Spectroscopy June 21, MHz window Spin-rotation (approx 180 MHz) Asymmetry doubling (K=3 collapsed) U lines

65 th International Symposium on Molecular Spectroscopy June 21, 2010 *Spin-rotation components not shown *K=1 flank out, other components compressed

65 th International Symposium on Molecular Spectroscopy June 21, 2010  0.5% CH 3 OH in Ar pulsed at 45psi, Zn laser ablated, DC discharge assisted (1100 V) Instrumentation  Fabry-Perot cavity, aluminum mirrors and antennae for emitting and receiving  4-40 GHz MW synthesizer  Pulsed-valve nozzle 40° to mirror axis with ablation part  532 nm Surelite I-10 Nd:YAG laser  Frequency at 10Hz

65 th International Symposium on Molecular Spectroscopy June 21, ZnOH (X 2 A’) 1.8 MHz 250 shots

65 th International Symposium on Molecular Spectroscopy June 21, transitions across 200 GHz 3 isotopes 64 ZnOD 66 ZnOD 68 ZnOD 500 lines for fit

65 th International Symposium on Molecular Spectroscopy June 21, 2010 H eff = H rot + H sr + H mhf

65 th International Symposium on Molecular Spectroscopy June 21, 2010

65 th International Symposium on Molecular Spectroscopy June 21, 2010  114 °, covalent character, significant sterics, unpaired electron on Zn  O-H bond distance (H acidity)  Zn-O increased bond length  Zn radius smaller that Cu  but bigger angle opposite from CuOH/AgOH (H+/ M+ repulsion)  H destabilizes Zn-O bond for ligand exchange or insertion chemistry  Agreement with theory

65 th International Symposium on Molecular Spectroscopy June 21, 2010 Fermi contact term Existence of fermi contact term points to 4s character Small fermi contact term consistent with Zn--H coupling But why negative: supports delocalized non-bonding MOs that affect spin density at H directly Dipolar term Points to significant d character sd hybridization (electron correlation among d-orbitals necessary for CuOH/AgOH calculations)

65 th International Symposium on Molecular Spectroscopy June 21, 2010  Synthesized ZnOD using D 2 O for direct millimeter absorption, and using CH 3 OH for FTMW DALAS  Identified 64 ZnOD, 66 ZnOD, and 68 ZnOD  Determined constants ZnOD/ZnOH  Determined structure for ZnOH  Bent structure (114°)  Covalent bonding character  Future  ZnSH, ZnCCH  Trends in 3d hydroxides on to Ni, Co, Fe

65 th International Symposium on Molecular Spectroscopy June 21, 2010  Professor Lucy M. Ziurys  Lindsay N. Zack  Matthew P. Bucchino  Ming Sun  Dennis Clouthier  Ziurys research group  Funding: NSF and NASA