01520nas a2200277 4500008004100000022001400041245013900055210006900194260000900263300001400272490000900286520054500295653002900840653002500869653000900894653004000903653001900943653003200962100002400994700001801018700001801036700001901054700001701073700002001090856013201110 2020 eng d a1434-193X00aVinylogous michael addition of 3-alkylidene-2-oxindoles to beta,gamma-unsaturated alpha-keto esters by bifunctional cinchona alkaloids0 aVinylogous michael addition of 3alkylidene2oxindoles to betagamm cSEP  a5690-56940 v20203 a

A highly enantioselective vinylogous Michael addition of 3-alkylidene-2-oxindoles with beta,gamma-unsaturated alpha-keto esters using a bifunctional tertiary-amine thiourea catalyst is demontsrated. The challenging Michael reaction with the beta,gamma-unsaturated alpha-keto esters has been accomplished due to the synchronized H-bond guided dual activation of vinylogous nucleophile and electrophile by catalyst. The reaction afforded product in high yield while resulting in excellent stereocontrol (> 19:1E/Zand upto 99 %ee).

10a3-Alkylidene-2-oxindoles10aAsymmetric synthesis10abeta10agamma-Unsaturated alpha-keto esters10aMichael adduct10aVinylogous Michael addition1 aJaiswal, Manish, K.1 aKumar, Rajesh1 aSingh, Sanjay1 aJain, Shailija1 aVanka, Kumar1 aSingh, Ravi, P. uhttps://library.ncl.res.in/content/vinylogous-michael-addition-3-alkylidene-2-oxindoles-betagamma-unsaturated-alpha-keto-esters01959nas a2200193 4500008004100000022001400041245015000055210006900205260000800274300001600282490000700298520124400305100001701549700001701566700001901583700001701602700001901619856012701638 2022 eng d a1477-922600aVersatile chemistry of six-membered NHC with boranes: bromination at sp(3) borane, activation of the B-H bond of HBpin, and ring expansion of NHC0 aVersatile chemistry of sixmembered NHC with boranes bromination  cOCT a14452-144570 v513 a

The NHC.borane chemistry has been majorly restricted to imidazol-2-ylidene classes of carbenes. In our previous communication, we reported the synthesis of 6-SIDipp center dot BH3 [6-SIDipp = 1,3-di(2,6-diisopropylphenyl) tetrahydropyrimidine-2-ylidene] and its electrophilic substitution reaction with iodine. Here, we have shown selective bromination of a 6-SIDipp stabilized sp(3) B-H bond. Treatment of 1.2 equivalents of N-bromosuccinamide with 6-SIDipp center dot BH3 gives a mixture of mono- and disubstituted products 6-SIDipp center dot BH2Br (1) and 6-SIDipp center dot BHBr2 (2). However, the reactions with alkyl bromides or carbon tetrabromide resulted in 6-SIDipp center dot BH2Br (1) selectively. Exploration of the chemistry of 6-SIDipp with BHCl2 and 9-BBN (9-borabicyclo[3.3.1]nonane) led to mono-6-SIDipp adducts 3 and 6a. Furthermore, 6a undergoes ring expansion to afford a seven-membered product, 6b, under mild conditions. Unlike BHCl2 or 9-BBN, the B-H bond of HBpin undergoes oxidative addition upon reaction with 6-SIDipp, epitomizing the first example (7) of a B-H bond insertion at NHCs. The analogous reactivity with HBcat led to a tetra-hydropyrimidinium salt with B(cat)(2) as a counteranion (8).

1 aKundu, Gargi1 aDixit, Ruchi1 aTothadi, Srinu1 aVanka, Kumar1 aSen, Sakya, S. uhttps://library.ncl.res.in/content/versatile-chemistry-six-membered-nhc-boranes-bromination-sp3-borane-activation-b-h-bond01964nas a2200253 4500008004100000022001400041245011800055210006900173260000800242490000600250520107500256653002001331653001901351653003101370653002501401653001901426100001801445700002701463700001701490700001701507700003001524700002701554856012901581 2023 eng d a2367-093200aVisible-light-active unsymmetrical squaraine dyes with 1 V of open-circuit voltage for dye-sensitized solar cells0 aVisiblelightactive unsymmetrical squaraine dyes with 1 V of open cMAY0 v73 a

A series of alkyl-group-functionalized, aniline- and indoline-donor-based, unsymmetrical visible-light-active squaraine dyes, AM1-3, were designed and synthesized. Dye-sensitized solar cell (DSSC) devices were fabricated with both I-/I-3(-) and [Cu(tmby)(2)](+/2+) electrolytes. DSSC devices sensitized with the AM1 and AM2 dyes showed relatively high-power conversion efficiency of 7.44 % and 7.22 %, respectively with I-/I-3(-) in the absence of chenodeoxycholic acid (CDCA) than those of the AM3 dye (5.41 %). The [Cu(tmby)(2)](+/2+) electrolyte along with poly(3,4-ethylenedioxythiophene) (PEDOT) as cathode material showed excellent open-circuit potentials (V-OC) of 1030, 1025, and 1001 mV with the DSSC efficiency of 8.05 %, 7.96 %, and 5.84 %, respectively, for the AM1, AM2, and AM3 dyes in the absence of CDCA. Here, the AM1 dye exhibited the maximum DSSC efficiency of 8.05 % and V-OC of 1030 mV, which is the highest obtained efficiency and V-OC for the visible-light active zwitterionic unsymmetrical-squaraine dye with copper-based electrolyte.

10aCu electrolytes10adihedral angle10aDye-sensitized solar cells10aopen circuit voltage10asquaraine dyes1 aSingh, Amrita1 aSingh, Ambarish, Kumar1 aDixit, Ruchi1 aVanka, Kumar1 aKrishnamoorthy, Kothandam1 aNithyanandhan, Jayaraj uhttps://library.ncl.res.in/content/visible-light-active-unsymmetrical-squaraine-dyes-1-v-open-circuit-voltage-dye-sensitized02594nas a2200277 4500008004100000022001400041245017000055210006900225260000900294300001400303490000600317520158800323653002401911653002701935653003201962653001701994653002602011653001902037100001802056700002702074700001702101700001702118700003002135700002702165856012402192 2024 eng d a2574-096200aVisible, far-red, and near-infrared active unsymmetrical squaraine dyes based on extended conjugation within the polymethine framework for dye-sensitized solar cells0 aVisible farred and nearinfrared active unsymmetrical squaraine d cFEB  a1461-14750 v73 a

Alkyl group wrapped visible, far-red, and NIR active unsymmetrical squaraine dyes with pi-extension in the polymethine framework-based AM4-AM7 have been designed, synthesized, and utilized as sensitizers for dye-sensitized solar cells. To extend the pi-conjugation within the polymethine framework, thiophene moieties have been incorporated between the donor and acceptor moieties. Absorption spectroscopic studies revealed that pi-extension with each -C & boxH;C- unit resulted similar to 100 nm of redshift in the charge transfer transition with the lambda(maximum) of 541, 643, 747, and 833 nm for AM4, AM5, AM6, and AM7 dyes, respectively, with the molar extinction coefficient of >10(5) M(-1)cm(-1). The pi-extended conjugation-based AM6 and AM7 dyes showed improved light-harvesting efficiency (LHE), where the AM7 dye showed an LHE of 386 nm at 60%. Electrochemical studies of AM dyes revealed that the HOMO energy level of the sensitizers has been modulated systematically. Further, pi-extension within the polymethine framework showed a dramatic effect on V-OC, J(SC), and device efficiency when move from visible active AM4 to far-red active to NIR active AM7 dyes. The DSSC efficiencies of 7.35, 5.18, 0.08, and 0.053% have been achieved with the I-/I-3(-) electrolyte (Z-50) for the AM4, AM5, AM6, and AM7 dyes, respectively. Further, AM4 dye has been cosensitized with AM5, AM6, and AM7 dyes, where AM4:AM5 (1:1) composition achieved the maximum efficiency of 8.12% with I-/I-3(-) electrolyte (Z-50) compared to the other cosensitization compositions.

10aaggregation of dyes10aDSSC device efficiency10alight-harvesting efficiency10api-extension10apolymethine framework10asquaraine dyes1 aSingh, Amrita1 aSingh, Ambarish, Kumar1 aDixit, Ruchi1 aVanka, Kumar1 aKrishnamoorthy, Kothandam1 aNithyanandhan, Jayaraj uhttps://library.ncl.res.in/content/visible-far-red-and-near-infrared-active-unsymmetrical-squaraine-dyes-based-extended03762nas a2200265 4500008004100000022001400041245015300055210007000208260000800278300001600286490000600302520279600308653002003104653002003124653003103144653003003175653002803205100002403233700001603257700001703273700001703290700003003307700002703337856013203364 2025 eng d a2574-096200aVisible-light active π-extended unsymmetrical squaraine dyes for dye-sensitized solar cells: steric effects for controlling the aggregation of dyes0 aVisiblelight active πextended unsymmetrical squaraine dyes for d cOCT a15459-154700 v83 a

The dye-anchored TiO2 photoanode plays a vital role in the light harvesting and charge separation processes in dye-sensitized solar cells. Aggregation of dyes (H- and J-type) on the TiO2 surface is a facile process due to the presence of a periodical dye anchoring sites on the exposed facet of titania, and such self-assembled dye structures help broadening the absorption profile. However, photocurrent generation from such aggregated structure is a challenging task in dye-sensitized solar cell devices. Hence, controlling the dye aggregation on the TiO2 surface is an important aspect. Controlling the aggregation of dyes by which (i) an enhanced photocurrent generation (J SC) and (ii) enhanced V OC can be achieved by including the steric factors to the dye design principles, the steric factor in the sensitizer may help passivate the TiO2 surface to avoid the charge recombination process between electrons present in TiO2 and the oxidized electrolyte. On the other hand, extension of pi-conjugation in a sensitizer helps enhance the light absorption in the visible region besides modulating the HOMO and LUMO energy levels. Hence, synergizing both pi-extensions along with features that control the dye aggregation has been considered in designing visible active squaraine dyes. A thiophene pi-spacer was inserted in between a visible-light active unsymmetrical squaraine unit and a cyanoacetic acid acceptor unit to provide the AJ1 and AJ2 dyes. Though both the dye molecules possess a similar pi-framework, the AJ2 dye was functionalized with both in-plane and out-of-plane alkyl groups to decrease the aggregation of dyes on the TiO2 surface compared to AJ1. The AJ1 and AJ2 dyes absorbed at 560 nm with shoulder peaks appeared at 528 nm, which can be assigned to vibronic progression (1082 cm-1), and additional characteristic peaks of thiophene appeared at 392 nm with the molar extinction coefficient of 1.16-1.19 x 105 M-1 cm-1 in CH3CN. The LUMO and HOMO energy levels are well aligned with the conduction band of TiO2 and the redox potential of iodolyte (I-/I3 -) electrolyte with sufficient overpotentials for charge injection and dye regeneration processes, respectively. The highest DSSC device efficiency of 7.37% (J SC 14.44 mA/cm2, V OC 0.771 V, ff 67.1%) was achieved for the AJ2 dye with iodolyte (I-/I3 -) electrolyte in the presence of 2 equiv of optically transparent coadsorbent chenodeoxycholic acid (CDCA), which showed a good IPCE response in between 400 and 700 nm. Further, cosensitization of visible-light active AJ1, AJ2, and SQA10 dyes with a complementary far-red active SQS4 dyes showed the device efficiencies of 5.53% (AJ1:SQS4:CDCA), 7.14% (AJ2:SQS4:CDCA), and 7.18% (SQA10:SQS4:CDCA) with a good IPCE response in the 400-720 nm region.

10acosensitization10aDye aggregation10aDye-sensitized solar cells10api-extended squaraine dye10avisible-lightactivedyes1 aJadhav, Avinash, P.1 aSiby, Jesna1 aPandya, Rinu1 aVanka, Kumar1 aKrishnamoorthy, Kothandam1 aNithyanandhan, Jayaraj uhttps://library.ncl.res.in/content/visible-light-active-%CF%80-extended-unsymmetrical-squaraine-dyes-dye-sensitized-solar-cells