Greener protocol for one pot synthesis of coumarin styryl dy(7)

S.B.Phadtareetal./DyesandPigments97(2013)105e112

Table4

Comparisonofthespectralpropertiesofadye7awithrelatedanalogs.Solvent

Dye

NC

CN

111

NCCN

NOONOO

OO

NOO

7a

8910

lmax(nm)

lem(nm)

Stokeslmax(nm)

lem(nm)

Stokesshiftlmax(nm)

lem(nm)

Stokesshiftlmax(nm)

lem(nm)

StokesshiftAcetonitrile3824759342147756DMSO

389

488

99

e

e

e

Table5

Physicalproperties,molarextinctioncoef cientandrelative uorescencequantumyieldsofcompounds7ae7hinchloroform(10À4M).Entry

MolecularThermal

Molar

Quantumformula

stabilityin C

extinctionyield

coef cient( molÀ1dm3cmÀ1)7aC25H21N3O29829,7000.237bC26H23N3O327448,9000.117cC27H26N4O220737,8000.507dC31H25N3O327613,9000.397eC23H19N3O327261,7000.457fC24H20N4O226558,7000.317gC33H28N4O227550,2000.727hC37H38N4O225846,700

0.22

of0.11e0.72,withthehighestbeingshownforcompound7g,whichmaybeduetothepresenceoftheelectrondonatingabilityandstabilityofthecarbazoleringstructure.3.4.Thermalproperties

Thermalstabilityisde nedasthetemperatureuptowhichw95%ofthecompositionofthecompoundremainsstable.Thermalpropertiesofthecolorants7ae7hwereexaminedbythermogra-vimetricanalysis.Stepwiseisothermalrampingupto600 Cat10 C/minwasperformedinanitrogenatmosphere.Thechangeinweightofthecompoundwasmeasuredasafunctionoftempera-ture.Thermalstabilityofthecompounds7ae7hisshowninFig.5andtabulatedinTable5.Inthermogravimetricanalysis(TGA)thermograms,coumarindye7ashowed95%stabilityupto298 C.

Fig.5.Thermogravimetricanalysis.

shift35144089eeee

e

e

537

632

95

Allthesynthesizedcolorantswereobservedtohavethermalstability>200 C,whichmaybeattributedtotheplanararrange-mentofnitrilesprovidingadditionalrigiditytothemolecule.Thethermaldecompositionvaluesofthedyes7ae7hareprovidedinTable5andFig.5.4.Conclusion

Forthe rsttime,aseriesofstyryldyescontainingthe2-(1-(7-(diethylamino)-2-oxo-2H-chromen-3-yl)ethylidene)malononitrilemoietyweresynthesizedusingamodi edmethod.Thenewapproachinvolvedanef cient,onepotmethodologyfortherapidsynthesisofvariouscoumarinstyryldyesusingdeepeutecticsolvent.DESisinexpensive,easilyprepared,haslowviscosity,isbiodegradable,andcanactef cientlyasthesolventaswellasthecatalyst.Themethodwassimple,economicalandenvironment-friendlyapartfromresultinginhigheryieldandpurityoftheisolates.DESplayedthedualroleofcatalystaswellassolvent,therebynegatingtheuseofanyadditionalcatalyst.Thecolorantswerethoroughlyanalyzedbyspectralmethodsandsubjectedtophotophysicalandthermalstudies.Thenoveldyes7ae7hdis-playedexcellentphotoluminescentpropertiesandhighStokesshift.Theyalsoexhibitedhighthermalstabilityandcan ndapplicationsinphotoelectronics.Acknowledgments

AuthorsarethankfultoSAIFIIT-BombayandTataInstituteofFundamentalResearch,MumbaiforrecordingNMRspectraandCHNanalysis,TEQUIPforinstrumentalsupport.OneoftheauthorsisthankfultoCSIRforprovidingfellowship.AppendixA.Supplementarydata

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