1. Daniel P. Zaleski, Susanna L. Stephens, Nick R. Walker School of Chemistry, Bedson Building, Newcastle University, Newcastle upon Tyne, NE1 7RU, UK. Evidence from Broadband Rotational Spectroscopy for a Complex Between AgCCH and C 6 H 6 Anthony C. Legon School of Chemistry, University of Bristol, Bristol BS8 1TS, UK. The Ohio State 69 th International Symposium on Molecular Spectroscopy, June 20 th, 2014.

2. Metal Antitumor Agents In principle, three different groups of metal-containing antitumor agents can be distinguished:  inorganic complexes composed of a central metal atom surrounded inorganic ligands - been much clinical success against carcinomas of the head and neck  organometallic complexes containing one or more metal atoms as well as organic ligands, the ligands being linked to the metals by direct carbon-metal bonds  complexes also including metal atoms and organic ligands but lacking carbon-metal bonds - Antiproliferative activity against e.g. Ehrlich ascites tumor, sarcoma 180, B16 melanoma, colon 38 carcinoma, and Lewis lung carcinoma cisplatin Chem. Rev. 1987, 87, 1137-1152. Metallocene, M = Transition Metal

3. Benzene-AgX Complexes  Early-transition-metal compounds have shown tumor-inhibiting efficacy.  Mainly represented by metallocene complexes where M = Ti, V, Nb, Mo, Cu; and e.g., X = Cl  Focus on silver containing species: -Same column as Cu: similar electronic properties -Two isotopes ~50% abundance (important for structure determination) -Lacks quadrupolar nucleus -Experimentally easier to work with compared to other TM’s  Benzene is the classic biological analog. Angew. Chem., 1979, 91, 509. Angew. Chem., Znt. Ed. Engl., 1979, 18, 477. Z. Naturforsch. B: Anorg. Chem., Oig. Chem., 1979, 34B, 805. Z. Naturforsch. C Biosci., 1979, 34C, 1174. J. Znorg. Nucl. Chem., 1980, 42, 1789. ACS Symp. Ser., 1983, No. 209, 315.

4. Spectroscopy of Metal-Ringed Species JACS, 2004, 126,10981-10991. Vibrational/DFT study of Be-M + Organometallics, 1999, 18,1430-1438. Mass Spec study of Be-M TB01: Cp-ReCH 3 (CO)(NO)

5. Chirped Pulse FTMW Spectroscopy Broadband spectrometers with instantaneous frequency coverage from 2-8 GHz, 6.5-18.5 GHz, 18.5-26 GHz, and 25 – 40 GHz have been constructed. Current Technology: AWG24 Gs/s (12 GHz) Digital Oscilloscope 100 Gs/s (33 GHz)

6. ~60x ~3M FID’s ~100 hr

7. C 6 H 6 -AgCl ParameterExperiment* M062X aug-cc-pVTZ † B (MHz)867.5635(12)670.6502 DJ (kHz)0.03954(822)0.222 DJK (kHz)--0.198 χ aa (MHz) -24.2(14)-23.5 N lines 9- RMS (kHz)6.14- * C 6 H 6 - 107 Ag 35 Cl † Ag: aug-cc-pVTZ-PP Chem. Phys. Lett., 1997, 272, 61-68. 20 cm -1 Assigned Species C 6 H 6 - 107 Ag 35 Cl C 6 H 6 - 109 Ag 35 Cl C 6 H 6 - 107 Ag 37 Cl C 6 H 6 - 109 Ag 37 Cl C 6 H 5 D- 107 Ag 35 Cl C 6 H 5 D- 109 Ag 35 Cl

8. StructureA (MHz)B (MHz)C (MHz)B (MHz)DJ (kHz) Sym Top---867.56350.0350 Asym Top2642.9990868.6841866.4636867.57400.0868 C 6V 2805.2121791.8712 2*10^-9 Minimum2842.9929720.9477717.8263719.38720.1433 12589.3667759.6317739.6489749.64416.6401 22658.9544847.0038823.9803835.49278.8284 32875.3505933.7453905.1196919.425212.6019 43280.04921028.8637965.4478996.820348.3868 52648.1059728.7234710.4239719.57855.3386 62746.2920790.3695755.7916773.050617.9381 72948.2350852.9360792.6311822.442346.7579 83250.8617912.5184818.5120864.134991.0508 91733.27041003.2471815.4387867.1255168.0033 C 2V 5663.4018312.9461296.5590304.75551.5634 min-5A2756.622287.6286286.7459287.18730.0099 min-4.5A 2743.323336.5123335.1410 335.82670.0244 min-4A 2726.3418397.4721395.2479 396.36010.0663 C 6V -2.0A2830.6040856.7624 2*10^-9 tilted-2.0A2653.2633900.7231872.9112886.804413.0950 tilted-3.0A2424.3407603.6883580.6290592.15948.8153 tilted-4.0A2333.6614418.6347404.7867411.71493.0888 tilted-5.0A2235.4943296.8520288.1923292.52421.2018 Asymmetric Possibilities M062X/SDD

9. Structure Determination (A,B,C) = (I A,I B,I C ) I = Σ m i ∙r i 2 (A ˊ,B ˊ,C ˊ ) = (I A ˊ,I B ˊ,I C ˊ ) |r a |,|r b |,|r c | Isotopic substitution produces small (and predictable) shifts in the rotational constants that are site-specific. Free from other assumptions about the molecular structure Am. J. Phys. 1953, 21, 17. r(Be-Ag) = 2.043(9) Å r(Ag-Cl) = 2.240(7) Å MP2/aug-cc-pVTZ-PP

10. X-AgCl Trends J. Chem. Phys., 2011, 135, 024315. Species χ aa (MHz) r(Ag-Cl) (Å) AgCl-36.42.281 -Ar-34.52.285 -Kr-33.82.277 -Xe-32.22.271 -H 2 O-32.32.272 -NH 3 -29.82.263 -H 2 S-29.42.255 -C 2 H 2 -28.92.266 -OC-28.22.255 -C 2 H 4 -27.92.272 -C 6 H 6 -24.12.240 2.8 Å radius VDW (Ag) ~ 2.1 Å New J. Chem., 2007, 31, 832-834. r(Be-Ag) = 2.043(9) Å r(Ac-Ag) = 2.184(8) Å 0.254 -0.731 -0.432 0.432 MP2/aug-cc-pVTZ-PP

11. Recap Experiment r(Be-Ag) = 2.043(9) Å Theory calculates r(Be-Ag) = 2.195 Å Exp Theory Asym* Theory Sym* B (MHz)867.5635(12)756.8813833.1309 DJ (kHz)0.03954(822)-- DJK (kHz)--- χ aa (MHz) -24.2(14)-22.7-31.3 r(Ag-Cl) (Å ) 2.240(7)2.2452.266 * MP2/aug-cc-pVTZ Ag: aug-cc-pVTZ-PP

12. C 6 H 6 -AgCCH ~20x ~3M FID’s ~100 hr

13. C 6 H 6 -AgCCH 21 cm -1 ParameterExperiment* MP2 6-311++G(d,p) † B (MHz)791.03578(20)739.32668 DJ (kHz)0.0230(12)0.205 N lines 7- RMS (kHz)2.13- * C 6 H 6 - 107 AgCCH † Ag: cc-pVDZ-PP Assigned Species C 6 H 6 - 107 AgCCH C 6 H 6 - 109 AgCCH C 6 H 6 - 107 AgCCD C 6 H 6 - 109 AgCCD

14. Structure Determination (?) r(Ac-Ag) = 2.210(1) Å r(Ag-H) = 4.284(1) Å r(Be-Ag) ~ 3.0 Å r(Ag-H) = 4.367(2) Å J. Chem. Phys., 2014, 140, 124310.

15. Recap Experiment suggests r(Be-Ag) ~ 3.0 Å Theory calculates r(Be-Ag) = 2.194 Å Exp Theory Asym* Theory Sym † B (MHz)791.03578(20)739.32668843.4128 DJ (kHz)0.0230(12)0.205- DJK (kHz)-1.222- r(Ag-H) (Å ) 4.367(2)4.2704.256 * MP2/6-311++G(d,p) Ag: cc-pVDZ-PP † MP2/6-311++G(3df,3dp) Ag: aug-cc-pVTZ-PP

16. Conclusions  Be-AgX (X = Cl, CCH) likely has C 6v symmetry - Although Be-AgCCH remains uncertain  Strong overlap between the π-density and the Ag atom -Likely due to Ag atom size -Shorter Be-Ag distance than Ac-Ag (at least for AgCl) -Is there a system small enough to favor the ring edge?  Proper modeling left to do -Need frequency calculations -Ab initio seems to be underestimating the interaction

17. Acknowledgments Engineering and Physical Sciences Research Council AWE (Aldermaston ) University of Bristol David Tew Wataru Mizukami