Electronic Structure of Bis(4‐dimethylaminophenyl)squaraine

Divya, V.; Suresh, Cherumuttathu H.

doi:10.1002/slct.201803543

Cited by 3 publications

(5 citation statements)

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“…A significant common aspect is the large positive charge of the squarylium ring. This refutes the theoretical results recently obtained for a bis(4-dimethylaminophenyl)squaraine, numbered 1 in [18], which differs from the one in our study for the insertion of phenyl rings between the four-carbon ring and the bisdimethylamino groups. Those theoretical calculations suggest the location of positive charge on NMe 2 groups.…”

Section: Discussionsupporting

confidence: 89%

“…The positive charge of the squarylium ring exceeds +2e in all three molecules. Certainly, theoretical calculations on our squaraine at the same level of theory as that adopted for squaraine 1 [18], followed by topological analysis of the theoretical charge distributions of both, could help to clarify which is the more realistic description of the squarylium ring.…”

Section: Discussionmentioning

confidence: 99%

“…It is well documented that the role of electrostatics is essential to interpret the structural features of squaraine aggregates, as well as to understand unusual properties of centrosymmetric squaraines and the features of materials including squaraine frameworks [12][13][14], particularly the so-called quadrupolar dyes. Experimental as well as theoretical and computational work on these materials is published regularly [15][16][17][18][19].…”

Section: Introductionmentioning

confidence: 99%

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Experimental Charge Density Analysis and Electrostatic Properties of Crystalline 1,3-Bis(Dimethylamino)Squaraine and Its Dihydrate from Low Temperature (T = 18 and 20 K) XRD Data

Destro

Roversi

Soave³

et al. 2020

Crystals

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Multipolar refinements of structural models fitting extensive sets of X‐ray diffraction(XRD) data from single crystals of 1,3‐bis(dimethylamino)squaraine [SQ, C8H12N2O2] and itsdihydrate [SQDH, C8H12N2O2∙2H2O], collected at very low T (18 ± 1 K for SQ, 20 ± 1 K for SQDH),led to an accurate description of their crystal electron density distributions. Atomic volumes andcharges have been estimated from the experimental charge densities using the Quantum Theory ofAtoms in Molecules (QTAIM) formalism. Our analysis confirms the common representation (in theliterature and textbooks) of the squaraine central, four‐membered squarylium ring as carrying twopositive charges, a representation that has been recently questioned by some theoreticalcalculations: the integrated total charge on the C4 fragment is estimated as ca. +2.4e in SQ and +2.2ein SQDH. The topology of the experimental electron density for the SQ squaraine molecule ismodified in the dihydrated crystal by interactions between the methyl groups and the H2Omolecules in the crystal. Maps of the molecular electrostatic potential in the main molecular planesin both crystals clearly reveal the quadrupolar charge distribution of the squaraine molecules.Molecular quadrupole tensors, as calculated with the PAMoC package using both Stewart andQTAIM distributed multipole analysis (DMA), are the same within experimental error.

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Section: Discussionsupporting

confidence: 89%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Experimental Charge Density Analysis and Electrostatic Properties of Crystalline 1,3-Bis(Dimethylamino)Squaraine and Its Dihydrate from Low Temperature (T = 18 and 20 K) XRD Data

Destro

Roversi

Soave³

et al. 2020

Crystals

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“…An unusual aggregation system deviating significantly from the basic J- and H-picture is found for certain squaraine dyes. Due to their unique and easily customizable optical properties , this large family of π-conjugated quadrupolar molecules has attracted attention in recent experimental ,− and theoretical studies. − As reported, the molecules can easily form either J- or H-type aggregates depending on their molecular structure ,, and sample preparation conditions. ,,, Moreover, squaraines with a symmetric molecular backbone show strong electron-donating and -accepting properties, and both intra- and inter-molecular charge transfer could play an important role in the optical spectra of squaraine aggregates . Recently, a family of n -alkyl aniline squaraines (see Figure a) was synthesized and engineered , for organic solar cells which can reach relatively high power conversion efficiencies.…”

Section: Introductionmentioning

confidence: 99%

Structural Disorder as the Origin of Optical Properties and Spectral Dynamics in Squaraine Nano-Aggregates

et al. 2022

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In contrast to regular J-and H-aggregates, thin film squaraine aggregates usually have broad absorption spectra containing both J-and H-like features, which are favorable for organic photovoltaics. Despite being successfully applied in organic photovoltaics for years, a clear interpretation of these optical properties by relating them to specific excited states and an underlying aggregate structure has not been made. In this work, by static and transient absorption spectroscopy on aggregated n-butyl anilino squaraines, we provide evidence that both the red-and blue-shifted peaks can be explained by assuming an ensemble of aggregates with intermolecular dipole−dipole resonance interactions and structural disorder deriving from the four different nearest neighbor alignments�in sharp contrast to previous association of the peaks with intermolecular charge-transfer interactions. In our model, the next-nearest neighbor dipole−dipole interactions may be negative or positive, which leads to the occurrence of J-and Hlike features in the absorption spectrum. Upon femtosecond pulse excitation of the aggregated sample, a transient absorption spectrum deviating from the absorbance spectrum emerges. The deviation finds its origin in the excitation of two-exciton states by the probe pulse. The lifetime of the exciton is confirmed by the band integral dynamics, featuring a single-exponential decay with a lifetime of 205 ps. Our results disclose the aggregated structure and the origin of red-and blue-shifted peaks and explain the absence of photoluminescence in squaraine thin films. Our findings underline the important role of structural disorder of molecular aggregates for photovoltaic applications.

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“…Las escuaraínas (Kitson, 2017) son compuestos producidos por la condensación del ácido escuárico 1 con 2 moléculas ricas en electrones tales como anilinas, fenoles, pirroles e indoles, denotados como X en la Figura 1. Aunque la representación alterna del anillo central de estos compuestos zwitteriónicos (Figura 1, A) es una estructura aromática con doble carga positiva (Figura 1, B), recientemente ha sido rebatida en base a estudios teóricos que indican que la polarización de este anillo en realidad desplaza la carga positiva a los grupos sustituyentes (Divya, 2019) Figura 1. Estructura general de escuaraínas La principal característica física de estos compuestos es la intensa absorción de luz que ocasiona la emisión de fluorescencia.…”

Section: Introductionunclassified