Probing the energy landscapes of moleculesTheenergiesofmolecularmotions,suchasrotationandvibration,areunique fingerprintsofacompound.Withsupportfrommoderncompuationalchemistrymethods,weapplystate-of-the-artultrahighresolutionspectroscopictechniques toprobethelowestenergymotionsofmolecules.Spectrarecordedinthefar-infraredregionusingsynchrotronlightfromtheCanadianLightSourceprovide measuresofmolecularvibrationswithunprecedenteddetailwhileourcustom-builtmicrowavespectrometersattheUniversityofManitobashedlighton rotations and molecular re-arrangements. Our research fits under a number of diverse themes including (but not limited to):
Driving forces of conformational equilibriaYouprobablyrememberfromyourintroductorychemistryclassesthatmolecules canadoptdifferentgeometriesdependingontheirarrangementaroundsingleand doublebonds,butdidyouknowthateachformhasitsowndistinctrotational spectrum?Fordiallylamine,forexample,wehaveshownthatthereare42possible geometriesdependingonthepositionsofthetwosidechainsrelativetothe centralNHfunctionalgroup.Weidentifiedspectralfingerprintsofthefourlowest energyformsandfoundthattherichconformationalmixtureisaresultofacareful balance of hyperconjugative and steric effects. Astrochemical signaturesDidyouknowthatastronomersusemicrowaveandinfraredspectratoidentifynew speciesinspace?WegeneratepotentialcandidatesinthelabsuchasHCCNCSand HCCCCNCSusinghighvoltageelectricdischargesourcesandrecordtheir microwaveandinfraredspectraforinclusioninastronomycatalogs.Eachnew detectioninspaceprovidesanotherpieceinthepuzzleofthechemicalevolution of the Universe.Accurate molecular geometriesDoyouknowhowscientistsfindthebondlengthsandanglesofamoleculewith greataccuracyandprecision?TheyuseMolecularRotationalResonance(MRR) spectroscopy,theelectricfieldanalogofNMRspectroscopy.Wehavetwo instrumentsinourlabthatallowustomeasureeventhemostsubtlechangesin moleculargeometry.Wecanevenshowthepreferenceforoneresonancestructure over another as in our studies on fluorinated rings of anisole and benzaldehyde.Microsolvation Didyoueverconsiderhowthepropertiesofamoleculechangewhensolvent moleculespackaroundit?Ourspectrahelpusidentifythelowestenergybinding sitesforsolvent,whichconformersaremoreeasilysolvatedandthedynamicsof thesolvent-soluteinteraction.Inourstudyofthemicrosolvationofthiophene,for example,weidentifiedtwofaciletunnellingmotionsinvolvingthewaterhopping across the ring and rotating about its symmetry axis.
Probing the energy landscapes of moleculesTheenergiesofmolecularmotions,suchasrotationandvibration,are uniquefingerprintsofacompound.Withsupportfrommodern compuationalchemistrymethods,weapplystate-of-the-artultrahigh resolutionspectroscopictechniquestoprobethelowestenergymotions ofmolecules.Spectrarecordedinthefar-infraredregionusing synchrotronlightfromtheCanadianLightSourceprovidemeasuresof molecularvibrationswithunprecedenteddetailwhileourcustom-built microwavespectrometersattheUniversityofManitobashedlighton rotations and molecular re-arrangements. Ourresearchfitsunderanumberofdiversethemesincluding(butnot limited to):
Driving forces of conformational equilibriaYouprobablyrememberfromyourintroductorychemistryclassesthat moleculescanadoptdifferentgeometriesdependingontheir arrangementaroundsingleanddoublebonds,butdidyouknowthat eachformhasitsowndistinctrotationalspectrum?Fordiallylamine,for example,wehaveshownthatthereare42possiblegeometries dependingonthepositionsofthetwosidechainsrelativetothecentral NHfunctionalgroup.Weidentifiedspectralfingerprintsofthefour lowestenergyformsandfoundthattherichconformationalmixtureisa result of a careful balance of hyperconjugative and steric effects. Astrochemical signaturesDidyouknowthatastronomersusemicrowaveandinfraredspectrato identifynewspeciesinspace?Wegeneratepotentialcandidatesinthe labsuchasHCCNCSandHCCCCNCSusinghighvoltageelectricdischarge sourcesandrecordtheirmicrowaveandinfraredspectraforinclusionin astronomycatalogs.Eachnewdetectioninspaceprovidesanotherpiece in the puzzle of the chemical evolution of the Universe.Accurate molecular geometriesDoyouknowhowscientistsfindthebondlengthsandanglesofa moleculewithgreataccuracyandprecision?TheyuseMolecular RotationalResonance(MRR)spectroscopy,theelectricfieldanalogof NMRspectroscopy.Wehavetwoinstrumentsinourlabthatallowusto measureeventhemostsubtlechangesinmoleculargeometry.Wecan evenshowthepreferenceforoneresonancestructureoveranotheras in our studies on fluorinated rings of anisole and benzaldehyde.Microsolvation Didyoueverconsiderhowthepropertiesofamoleculechangewhen solventmoleculespackaroundit?Ourspectrahelpusidentifythe lowestenergybindingsitesforsolvent,whichconformersaremore easilysolvatedandthedynamicsofthesolvent-soluteinteraction.In ourstudyofthemicrosolvationofthiophene,forexample,weidentified twofaciletunnellingmotionsinvolvingthewaterhoppingacrossthe ring and rotating about its symmetry axis.