Ion and Neutral Thermochemistry from the Gas to Solution Phase an overview Tomas Baer University of North Carolina Chapel Hill, NC Mesilla Workshop on Organometallic Chemistry

Ion and Neutral thermochemistry – Gas Phase ML 2 ML + L M + 2L ML 2 + ML + + L M + + 2L Known IE(M) Lichtenberger Yang Yang Sztáray Armentrout Baer Sztáray Derived

Ionization Energy Measurements IE ad  H ion  Electron Energy IE ad ? Uncertainty = 0.10eV (10 kJ/mol) IE ad  Electron Energy IE ad Uncertainty = 0.01eV (1 kJ/mol) Molecular beam cooling – laser ionizationRoom Temperature PES

Thermal energy and Breakdown Diagram EoEo Photon energy (hv) E o -hv P+P+ D+D+ E o ± 10 meV (1 kJ/mol) hv E o -hv P(E) E o P + AB + Fractional Abundance Known thermal energy distribution TPEPICO experiment No worries about FC factors

Dissociation Onset Measurements Collisional Dissociation - Armentrout Collision energy (eV) AB + A + + B  H dis E0E0 E 0 ± 50 meV (5 kJ/mol) A + signal AB + + M  A + + B + M Again, no worries about FC factors. But there are other worries such as dissociation rate constants.

(C 6 H 6 ) 2 Cr Breakdown diagram BzCrBz +  CrBz + + Bz  Cr Bz Li and Baer, J. Phys. Chem. A (2002) BzCrBz BzCrBz + CrBz + + Bz E int (Bz) + E trans hvhv

Energy partitioning in dissociation E0E0 E E-E 0 EiEi PEt 3 +  HPEt C 2 H 4 Need only product vibrational frequencies. No adjustable parameters involved.

(C 6 H 6 ) 2 Cr Energetics Measured IE (laser spectrosc.) Kurikawa et al. (1999) Organometallics18, s 3d 3d 3d 3d 3d Cr Measured IE (laser spectrosc.) D.S. Yang (unpublished) 5.465eV

Solvation Effects in neutral organometallic complexes ML n ML n-1 + L ML n-1 SML n-1  S + L  S SML n-1 ML n-1 + L ML n (g) fHofHo BE[M-L(g)] ML n  S BE[M-L(s)] SE(SML n-1 + L ) BE[M-S(g)] Gas Phase Solution Phase photoacoustic calorimetry Ted Burkey & Joe Grabowski transient IR spectroscopy Eric Weitz CID, PEPICO, PES Baer/Sztáray/Armentrout Lichtenberger/Yang Theory: Chris Cramer; Tom Ziegler; Mu-Hyun Baik SE(ML n )