Photophysical and Photochemical Properties and Aggregation Behavior of Phthalocyanine and Naphthalocyanine Derivatives

Abstract

The photophysical and photochemical properties of phthalocyanine and naphthalocyanine with similar structures were studied in solution and with density-functional theory (DFT) computational method. The extended π-conjugated system in naphthalocyanines causes a bathochromic shift in UV-Vis, emission and excitation bands, and promotes lesser generation of singlet oxygen in solution when compared to phthalocyanines. Time dependent DFT (TD-DFT) calculations point out the molecular orbitals involved in Q-band transition, corresponding to highest occupied molecular orbital (HOMO) to lowest unoccupied molecular orbital (LUMO) transition with a concentration of charge along x-axis, while the transition to LUMO+1 is in y-axis direction. The presence of tert-butyl substituents does not affect the molecular orbitals shape, but affect their energies. Aggregation studies in dimethyl sulfoxide (DMSO):water solutions showed that naphthalocyanines studied have more aggregation tendency than the phthalocyanines. DFT studies indicated that stacked-dimers are preferred to rotated-stacked conformation due the interaction between Zn II and nitrogen atom from different monomers.

Photophysics of Zinc 2,11,20,29-Tetra-tert-butyl-2,3-Naphthalocyanine: Aggregation-Induced S2 Emission and Rapid Intersystem Crossing in the Solid State

“…The optical properties of ZnNc and those of its tert -butyl-modified derivative t -Bu-ZnNc have received much less attention . To exploit ZnNc and its derivatives as near-infrared-absorbing chromophores in electronic and electro-optic applications, a deeper understanding of their excited states is needed.…”

Dual Emissive Zn(II) Naphthalocyanines: Synthesis, Structural and Photophysical Characterization with Theory-Supported Insights towards Soluble Coordination Compounds with Visible and Near-Infrared Emission

“…As a consequence of their high tendency to form aggregates, a drop of fluorescence and singlet oxygen quantum yields is observed [ 30 , 31 ]. There have been several structural variations introduced to overcome the solubility and aggregation issues of (na)phthalocyanines, including the insertion of bulky substituents in the peripheral positions of the macrocycles [ 25 , 32 , 33 , 34 , 35 ], the addition of axial ligands to the central atom [ 28 , 30 , 36 , 37 , 38 , 39 ], or the encapsulation of the dye in colloidal particles [ 40 , 41 ]. Furthermore, peripheral functional groups in Ncs macrocycles may be utilized to further tailor intra- and intermolecular interactions as well as optical, photochemical, and electrochemical properties; particularly, aromatic groups increase intermolecular π - π interactions [ 19 , 34 ].…”

Synthesis of a Naphthalocyanine-Like Dye: The First Report on Zn(II)-1,6-methano[10]annulenecyanine

“…Near-infrared (NIR) dyes have received increasing attention due to their versatile applications in materials science [1][2][3][4][5], medical applications [6][7][8][9][10][11][12][13][14], catalysis and other advanced technology devices [12,[15][16][17]. In this context, phthalocyanines and naphthalocyanines are very robust dyes with relevant photophysical properties and must be highlighted [18][19][20][21][22][23].…”