Metal Crown-Porphyrin Complexes: Preparation, Optical Properties, and Applications (Review)

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Metal Crown-Porphyrin Complexes: Preparation, Optical Properties, and Applications (Review) A. Yu. Tsivadzea, * and A. Yu. Chernyad’eva, ** a

Frumkin Institute of Physical Chemistry and Electrochemistry, Russian Academy of Sciences, Moscow, 119071 Russia *e-mail: [email protected] **e-mail: [email protected]

Received May 27, 2020; revised July 7, 2020; accepted July 10, 2020

Abstract—The review addresses methods for the synthesis of metal complexes of crown-substituted porphyrins; structural features of these compounds; and the influence of metal cations on the luminescence and other photophysical properties of metal crown-porphyrin complexes. Thermochromic, fluorescence, and phosphorescence properties of metal crown-porphyrins are analyzed; the applicability of these compounds as luminescence-based temperature sensors, sensors for alkali metal cations, thermochromic materials, and active components of photovoltaic energy converters are considered. Keywords: crown ethers, porphyrins, metal cations, electronic absorption spectra, luminescence properties, fluorescence, phosphorescence, decay kinetics, supramolecular associates, thermochromism, luminescence-based temperature sensors, photovoltaic converters, bulk heterojunction DOI: 10.1134/S0036023620110194

INTRODUCTION SECTION I. Synthesis and Luminescence Characteristics of Metal Crown-porphyrin Complexes SECTION II. Supramolecular Structures based on Aluminum Crown-porphyrin and Their Optical Properties SECTION III. Luminescence Temperature Sensors based on Transition Metal Crown-porphyrin Complexes SECTION IV. Composite Photovoltaic Converters using Platinum Metal Crown-porphyrin Complexes in the Active Layer CONCLUSIONS INTRODUCTION Crown ethers are known to be organic compounds capable of efficient binding of alkali and alkaline earth metal cations [1–3] and lanthanide cations [4]. Crown ether moieties are also useful as building blocks for complex organic molecules, which can be assembled into various supramolecular structures upon reactions with alkali and alkaline earth metal cations [5–8]. By now, crown ethers (Fig. 1) have found use as phase transfer agents for salts insoluble in organic media, such as potassium permanganate; owing to crown ethers, KMnO4 can act as an oxidant in nonpolar organic solvents [9]. There are other applications of crown ethers such as selective extraction of lantha-

nides from chemically complex aqueous solutions [4] and separation of metal isotopes, which is attained by varying substituents at the carbon atoms of the crown ether rings, ensuring the stability of a particular crown ether conformation that favors selective binding of a definite metal isotope contrary to the Pedersen principle (simple size match between the metal ionic radius and the crown ether cavity) [7, 10–12]. Of certain interest is the replacement of crown ether oxygen atoms by nitrogen or sulfur atoms, which may ensure binding of transition metal cations by crown ether molecules [13–16]; therefore, such crown ethers are now widely use