acs.est.8b01189

acs.est.8b01189CommentonTheCaseAgainstChargeTransferInteractionsinDissolvedOrganicMatterPhotophysicsInthisrecentarticle,1theauthorsarguethatchargetransfer(CT)interactionscannotbeimportanttotheopticalpropertiesofhumicsubstances(HS)anddissolvedorganicmatterbecauseperturbationsofsolventtemperature,viscosityandpolaritydonotaffecttheabsorbanceandfluorescencespectrallineshapes.However,thisconclusionispredicatedonthreeveryimportantassumptions:(1)theelectrondonors(D)andacceptors(A)arefreelydiffusinginsolution;(2)theDandApairsareindynamicequilibriumwiththeDAcomplex;(3)theDandApairsandtheDAcomplexarecompletelysolventaccessible.Basedonthesethreeassumptions,theauthorsrightlyexcludethesimplemodelsshownintheirFigure1.However,allthreeoftheseassumptionsarequestionableforHSbasedonexistinginformation.First,workbyDreyeretal.2hasdemonstratedforcloselyrelatedmaterials(polydopamine)thatDandApairswillformhighermolecularweightaggregatesthatarestabilizedthroughacombinationofchargetransfer,π-stackingandhydrogen