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1、Articlepubs.acs.org/JACSStableAlkanesContainingVeryLongCarbon−CarbonBonds,⊥,‡⊥⊥⊥AndreyA.Fokin,*LesyaV.Chernish,PavelA.Gunchenko,EvgeniyaYu.Tikhonchuk,‡§∥∥,‡HeikeHausmann,MichaelSerafin,JeremyE.P.Dahl,RobertM.K.Carlson,andPeterR.Schreiner*⊥DepartmentofOrganicChemistry,KievPolytechnicInst
2、itute,pr.Pobedy37,03056Kiev,Ukraine‡InstituteofOrganicChemistry,Justus-LiebigUniversity,Heinrich-Buff-Ring58,D-35392Giessen,Germany§InstitutfürAnorganischeChemiederJustus-Liebig-Universitat,Heinrich-Büff-Ring58,D-35392Giessen,Germany∥StanfordInstituteforMaterialandEnergyScience,Geballe
3、LabforAdvancedMaterials,StanfordUniversity,Stanford,California94305,UnitedStates*SSupportingInformationABSTRACT:Themetal-inducedcouplingoftertiarydiamondoidbromidesgavehighlystericallycongestedhydrocarbon(hetero)dimerswithexceptionallylongcentralC−Cbondsofupto1.71Åin2-(1-diamantyl)[121
4、]tetramantane.Yet,thesedimersarethermallyverystableevenattemperaturesabove200°C,whichisnotinlinewithcommonC−Cbondlengthversusbondstrengthscorrelations.WesuggestthattheextraordinarystabilizationarisesfromnumerousintramolecularvanderWaalsattractionsbetweentheneighboringH-terminateddiamon
5、d-likesurfaces.TheC−Cbondrotationaldynamicsof1-(1-adamantyl)diamantane,1-(1-diamantyl)diamantane,2-(1-adamantyl)triamantane,2-(1-diamantyl)triamantane,and2-(1-diamantyl)[121]-tetramantanewerestudiedthroughvariable-temperature1H-and13CNMRspectroscopies.Theshapesoftheinward(endo)CHsurfac
6、esdeterminethedynamicbehavior,changingthecentralC−Cbondrotationbarriersfrom7to33kcalmol−1.Weprobetheabilityofpopulardensityfunctionaltheory(DFT)approaches(includingBLYP,B3LYP,B98,B3LYP-Dn,B97D,B3PW91,BHandHLYP,B3P86,PBE1PBE,wB97XD,andM06-2X)with6-31G(d,p)andcc-pVDZbasissetstodescribesu
7、chanunusualbondingsituation.Onlyfunctionalsaccountingfordispersionareabletoreproducetheexperimentalgeometries,whilemostDFTfunctionalsareabletoreproducetheexperimentalrotationalbarriersduetoerrorcancellations.Computationsonlargerdiamondoidsrevealthattheinterplaybetweentheshapesandthes
