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Densityfunctionalcalculations shownoncovalentinteractions drivingelectrocatalysis KlemensNoga1,3,PiotrP.Romańczyk2,Mariusz Radoń3,StefanS.Kurek2 1 AcademicComputerCenter CYFRONET,ul.Nawojki 11,30-950Kraków,Poland 2 MolecularElectrochemistryGroup,FacultyofChemicalEngineeringandTechnology, CracowUniversityofTechnology,ul.Warszawska 24,31-155Kraków,Poland 3 FacultyofChemistry,Jagiellonian University,ul.Ingardena 3,30-060Kraków,Poland [email protected],[email protected] Scientificinterests • Electrontransfermechanismbetweenredoxcentresin mixed-valencemolybdenumandtungstenscorpionates involvedinelectrocatalysis • Dissociativeelectrontransfer(DET)processesin dehalogenationoforganichalides • Roleofnoncovalentinteractionsinelectrocatalysis andDET processes • Computationalestimationofreductionandoxidation potentialsoftransitionmetalcomplexesandorganic compounds MoandWscorpionate alkoxides {MoII(NO)(TpMe2)}(OCH3)2 Reversibleredoxpotentialfine tunedbyalkoxy ligandRO- • Redoxpotentialof{MII/I(NO)(TpMe2)−Oalk}0/•− (M=MoorW)well reproducedbyDFT:B3LYP/LACV3P+/IEF-PCM: • {Mo−OMe}0/•− - calculated:1.80V,measured:1.84V • {W−OMe}0/•−- calculated:2.45V,measured:2.40V • Strongmetal-metalinteractions(uptoΔredE1/21440mV)inmixedvalencecompoundswithtwo{MoII–0(NO+)(TpMe2)}2+,1+,0 cores Electrocatalysis ofofCHCl3 dehalogenation by{MoI(NO)(TpMe2)(Oalkoxy)}•− Autocatalytic process ΔEred,CHCl3 ~1V ReductionofCHCl3by Hold-ramp-stepexperiment Inhibitionofreactionby {MoI(NO)(TpMe2)(Oalkoxy)}•− provingstabilityofcatalyst alkene • CHCl3 - fastautocatalyticprocess • CCl4 andC2Cl4 donotreactinthoseconditions,C2HCl5 andC2HCl3 typicalelectrocatalysis Roleof{MoII/I(NO)(TpMe2)(Oalkoxy)}•− in electrocatalysis - adducts DFT-D(COSMO/B3LYP-D3/def2-TZVPP)geometriesof {MoII/I(NO)(TpMe2)}(OCH3)2adductswithCHCl3 • Moscorpionates formweaklybondedadductswithCHCl3 through C−H···Oalkoxy hydrogenbondanddispersiveinteractions • AfterreductionofMocentre∆Ebind increases Roleof{MoII/I(NO)(TpMe2)(Oalkoxy)}•− in electrocatalysis - dehalogenation DFT-D(COSMO/B3LYP-D3/def2-TZVPP)geometriesof (a){MoI(NO)(TpMe2)}(OCH3)2•−···HCCl3adductwithelongatedC-Clbond(upto2.2Å)inCHCl3 (b){MoII(NO)(TpMe2)}(OCH3)2···HCCl2• adductafterDET • Weaklybonded{MoI(NO)(TpMe2)}(OCH3)2•−···HCCl3adductfacilitates electrontransfertochloroformcoupledwithC-Clbondcleavage Roleof{WII/I(NO)(TpMe2)(Oalkoxy)}•− inC2HCl5 andC2HCl4•dehalogenation DFT-D(COSMO/B3LYP-D3/def2-TZVPP)geometriesof (a){WI(NO)(TpMe2)}(OCH3)2•−···HC2Cl5adduct (b){WII(NO)(TpMe2)}(OCH3)2···HC2Cl4• adductafterDET • Weaklybonded{WI(NO)(TpMe2)}(OCH3)2•−···HC2Cl5 adductalsofacilitates electrontransfertopentachloroethane coupledwithC-Clbondcleavage Thermodynamical stabilityofadducts Adduct {MoII−Oalk}0···HCCl3 {MoI−Oalk}•−···HCCl3 {MoII−Oalk}0···HCCl2• {MoI−Oalk}•−···HC2Cl5 {MoI−Oalk}•−···HC2Cl3 {MoI−Oalk}•−···H2CCl2 {WI−Oalk}•−···HC2Cl5 {WII−Oalk}···HC2Cl4• {WI−Oalk}•−···HC2Cl4• {WI−Oalk}•−···HC2Cl3 {WI−Oalk}•−···H2CCl2 ∆Ebind −44.4 −52.3 −37.2 −53.6 −43.1 −37.7 −54.8 −46.4 −56.1 −44.4 −41.0 ∆Gbind 0.8 −6,7 6.3 −2.9 1.3 3.8 −5.0 1.7 −5.4 0.4 1.7 inkJ·mol−1 inCH2Cl2 solvent,BSSEcorrected • {MoI−Oalk}•−···HCCl3 and{WI−Oalk}•−···HC2Cl5stabilisationfacilitatesET • Lowerstabilityof{MoII−Oalk}0···HCCl2•and{WII−Oalk}···HC2Cl4•enables radicaldissociationandtriggersanothercatalyticloop MolecularcatalysisofCHCl3 andC2HCl3 reduction triggeredbyMo/Walkoxy scorpionates • CHCl3dehalogenation- twocatalyticloops,withautocatalyticreaction: 2CHCl3 +CCl2•− +3e− →CH2Cl2 +2CCl2•− +2Cl− • ForC2HCl3 evenmorecathodicWII/I redoxpotentialnotsufficienttoclose secondorganicloop Redoxpotentialsofcompoundsinvolved inC2HCl5 reduction Species E0calc(DFT-D) {WII−OMe}/{WI−OMe}•− −2.45 {WIII−OMe}•+/{WII−OMe} +0.68 C2HCl5/C2HCl4• +Cl− −0.66 C2HCl4•/C2HCl3 +Cl− +0.93 C2HCl3/cis-C2HCl2• +Cl− −1.66 cis-C2HCl2•/cis-C2HCl2− −0.42 cis-C2H2Cl2/cis-C2H2Cl• +Cl− −1.97 cis-C2H2Cl•/C2H2 +Cl− +0.99 C2Cl4/C2Cl4•− −2.32 (−2.14) C2Cl4/C2Cl3• +Cl− −1.57 C2Cl3•/C2Cl3− −0.24 C2HCl/C2H•···Cl− −2.12 C2HCl/C2H• +Cl− −2.72 C2HCl/C2H• +Cl− −2.72 E0calc(CC) – – −1.27(−1.01) +0.80 −2.12(−1.86) −0.48 −2.36(−2.10) +0.91(+1.18) −2.66(−2.48) −2.09(−1.82) −0.24 −2.55(−2.32) −2.94(−2.68) −2.94(−2.68) E0exp −2,40 +0.63 (−0.98) (−1.86) (−2.09) (−2.11) (−1.73) inVvsFc,obtainedinCH2Cl2 solvent(orDMF) • SignificantdifferencesbetweenDFT-DandCCresultsonlyinthecaseof dissociativereduction(duetoerrorsinestimationofC-ClbondstrengthinDFT) Inhibitionofcatalysis DFT-D(COSMO/B3LYP-D3/def2-TZVPP)geometriesof (a)alcohol adduct,(b)alkeneadduct • AlcoholsformstrongerhydrogenbondthanCHCl3 andblockthebindingsite • Alkenesand DMFarebondedsignificantlyweakerthanCHCl3 • whenaddedingreatexcess • inhibitionoccurs bytrappingoftransientCHCl2•radicalbyalkeneor:CCl2byDMF Roleofnoncovalentinteractionsin electrocatalycis ComparisonofDFT-D(sharp,Clatomsyellow)andDFT(diffused,Clatomsgreen) (a){MoII−Oalk}··HCCl3, (b){MoI−Oalk}•−···HCCl3,(c){MoI−Oalk} 0···HCCl2• • Significantdifferencesinadductsgeometries,especiallyin{MoI−Oalk} 0···HCCl •,wherehydrogenbondisweakerandhasdispersivecharacter 2 • Noncovalentinteractionsarecrucialforstabilisationofadductswith weakhydrogenbond Roleofnoncovalentinteractionsin electrocatalysis Adduct {MoII−Oalk}0···HCCl3 {MoI−Oalk}•−···HCCl3 {MoII−Oalk}•−···HCCl2• {MoI−Oalk}•−···HOCH3 {MoI−Oalk}•−···HC(=O)N(CH3)2a {WI−Oalk}•−···H2C=CHCH3 DFT 4.2 −4.2 2.1 −22.2 10.5 12.6 DFT//DFT-D3 −32.2 −42.7 −23.8 −52.3 −22.6 −11.3 DFT-D3 Opt −44.4 −52.3 −37.2 −56.1 −30.1 −22.6 ∆Gbind inkJ·mol−1 inCH2Cl2 solvent(a inDMF),BSSEcorrected • Noncovalentinteractionsarecrucialforstabilisationofadductswith weakhydrogenbond • Even{MoI−Oalk}•−···HOCH3 adductwithstrongH-bondshows stabilisationeffectfromdispersiveinteractions • GeometryoptimizationusingDFT-D3stronglyrecommended Softwareremarksandcomputationaldetails • Gaussian03andGaussian09 • usedforDFTgeometryoptimizationsandredoxpotentialscalculations • widespectrumofsolvationmethods • Turbomole 6.xand7.x • usedforDFT-D3geometryoptimizations • veryfastingeometryoptimizationsandBSSEestimations • onlynumericalfrequenciescalculationswhenCOSMOmodelisused • embarrassinglyparallelbutconsumebigamountofresources(upto120cores forweek) • Molpro 2012and2015 • usedforparallelCCSD(T)calculations • canconsumegreatamountofresources(upto200coresforweeks)dueto scalingfactorofO(N7) Outcome • Rationalizedmechanismofelectrocatalytic dehalogenationof polychloroalkanes byMoandWscorpionate alkoxides anditsinhibition • combinedactionofC−H···Oalk bondingandCl···πpyrazolyl dispersiveinteractionsmay facilitateintramolecularelectrontransfer • Shownthatdispersioninteractionscouldbecrucialforstabilisationof weaklybondedadducts • DFT-Dhastobeusedinsuchcasestoyieldreasonableresults • Establishedcomputationalprotocolforcalculationofredoxpotentials forinvestigatedMo/Walkoxides andfororganicchlorideswiththe accuracyofupto0.05V • ComputationalresourceshavebeenprovidedbyACCCyfronet AGH whichispartofPLGrid Infrastructure Publications • P.P.Romańczyk,M.Radoń,K.Noga,S.S.Kurek,Autocatalyticcathodic dehalogenationtriggeredbydissociativeelectrontransferthrougha C−H···Ohydrogenbond,Phys.Chem.Chem.Phys. 15(2013)17522. • P.P.Romańczyk,K.Noga,M.Radoń,G.Rotko,S.S.Kurek,Ontheroleof noncovalentinteractionsinelectrocatalysis.Twocasesofmediated reductivedehalogenation,Electrochim.Acta,110(2013)619. • P.P.Romańczyk,G.Rotko,K.Noga,M.Radoń,G.Andryianau,S.S.Kurek, TheeffectofC−H···ObondingandCl···πinteractionsinelectrocatalytic dehalogenationofC2chloridescontaininganacidichydrogen, Electrochim.Acta 140(2014)497.