Conjugated macrocyclic materials with photoactivated optical absorption for the control of energy transmission delivered by pulsed radiations

Abstract

The control of the transmission of the energy transported by optical waves is of extreme importance for the realization of those advanced technologies which require high speed of operation and fast switching. Such a task can be approached through the design and preparation of materials that possess modulable optical properties. In the present review the aspect of material science behind the realization of the effect of optical limiting, OL (or optical power limiting, OPL), will be considered focusing on those materials based on conjugated metallo-macrocycles like porphyrins, phthalocyanines and derivatives. The choice of these molecular materials for OL purposes is motivated by the fact that the optical properties of such annulated systems can be finely modulated in a controlled fashion by changing the chemical structure of the complex. These changes involve the variation of the central metal, the extent of electronic conjugation of the ring, the nature and the number of peripheral ligands, and the eventual introduction of axial ligands coordinated by a central metals with a valence higher than +2. An attempt will be made to establish relationships between the structure of the macrocyclic complex and the relative OL properties taking into account the most recent developments in the field. During this analysis we will also discuss the aspect of optically passivity, i.e. the characteristic of the OL materials of undergoing fast changes of optical properties according to an internal mechanism of self-activation.

Phthalocyanines: An Old Dog Can Still Have New (Photo)Tricks!

“…Nonlinear optics (NLO) are an example of such a technological application, where phthalocyanines may play a prominent role, motivated by the fact that the optical properties of such annulated systems can be finely modulated in a controlled fashion by changing the chemical structure of the complex. These changes involve the variation of the central metal, the extent of electronic conjugation of the ring, the nature and the number of peripheral ligands, and the eventual introduction of axial ligands coordinated by central metals with a valence higher than +2 [ 64 , 65 , 139 , 140 ]. The definition of NLO mechanisms can be seen in references [ 64 , 65 ].…”

“…These changes involve the variation of the central metal, the extent of electronic conjugation of the ring, the nature and the number of peripheral ligands, and the eventual introduction of axial ligands coordinated by central metals with a valence higher than +2 [64,65,139,140]. The definition of NLO mechanisms can be seen in references [64,65].…”

“…Aware of the importance of phthalocyanine-related molecules, such as subphthalocyanines, naphthalocyanines, porphyrazines, and porphyrinoids, the recent discoveries (in the last five years) will solely consider the application of phthalocyanines in photonic-based materials technologies. Indeed, there are several highly cited review records in several sub-fields, e.g., photomedicine [ 50 , 51 , 52 , 53 , 54 , 55 , 56 , 57 , 58 , 59 , 60 ], photovoltaics [ 61 , 62 , 63 ], nonlinear optics [ 64 , 65 , 66 ], photocatalysis [ 67 , 68 , 69 ], among other photo-applications [ 70 , 71 , 72 ], portraying phthalocyanines among the therein discussed materials/molecules. Herein, more than a comprehensive view on the recent discoveries, a critical review of the most acclaimed/considered reports (i.e., most cited) was the driving force in this work, aiming to provide a brief and direct insight on the latest milestones in phthalocyanine science.…”

Ultrafast Nonlinear Optical Characteristics of Pyrene-Conjugated Azaphthalocyanines with Optical Limiting Behavior

“…Optical limiting is the reduction of the intensity of a transmitted beam when the incident beam intensity increases beyond a specific value. The optical limiting threshold is the most significant parameter in optical limiting applications, 7 where a lower limiting threshold indicates a better nonlinear optical material. Consideration of both the nonlinear optical absorption and nonlinear refraction properties enables characterization of the material criteria for ultrafast optical switching applications, i.e., evaluation using figures of merit.…”

A New Tool in the Quest for Biocompatible Phthalocyanines: Palladium Catalyzed Aminocarbonylation for Amide Substituted Phthalonitriles and Illustrative Phthalocyanines Thereof

“…In particular, phthalocyanines largely fulfil a crucial optical requisite, necessary for photomedicinal applications, which is a strong absorption in near-infrared (NIR) spectral region (600-900 nm), as light in this region affords the deepest penetration in soft tissue. These highly stable compounds, possessing high molar absorptivity, high quantum yields of fluorescence and structural versatility [4,13,14], can be conveniently modified to grant suitable biological solubility [15][16][17][18], by introduction of hydrophilic moieties in the structure. The majority of the moieties used so far are negatively charged, such as sulfonates or carboxylates [15,19] or positively charged, like quaternized amines [15,20].…”