Schiff Base Ancillary Ligands in Bis(diimine) Copper(I) Dye-Sensitized Solar Cells

Abstract

Five 6,6′-dimethyl-2,2′-bipyridine ligands bearing N-arylmethaniminyl substituents in the 4- and 4′-positions were prepared by Schiff base condensation in which the aryl group is Ph (1), 4-tolyl (2), 4-tBuC6H4 (3), 4-MeOC6H4 (4), and 4-Me2NC6H4 (5). The homoleptic copper(I) complexes [CuL2][PF6] (L = 1–5) were synthesized and characterized, and the single crystal structure of [Cu(1)2][PF6]·Et2O was determined. By using the “surfaces-as-ligands, surfaces-as-complexes” (SALSAC) approach, the heteroleptic complexes [Cu(6)(Lancillary)]+ in which 6 is the anchoring ligand ((6,6′-dimethyl-[2,2′-bipyridine]-4,4′-diyl)bis(4,1-phenylene))bis(phosphonic acid)) and Lancillary = 1–5 were assembled on FTO-TiO2 electrodes and incorporated as dyes into n-type dye-sensitized solar cells (DSCs). Data from triplicate, fully-masked DSCs for each dye revealed that the best-performing sensitizer is [Cu(6)(1)]+, which exhibits photoconversion efficiencies (η) of up to 1.51% compared to 5.74% for the standard reference dye N719. The introduction of the electron-donating MeO and Me2N groups (Lancillary = 4 and 5) is detrimental, leading to a decrease in the short-circuit current densities and external quantum efficiencies of the solar cells. In addition, a significant loss in open-circuit voltage is observed for DSCs sensitized with [Cu(6)(5)]+, which contributes to low values of η for this dye. Comparisons between performances of DSCs containing [Cu(6)(1)]+ and [Cu(6)(4)]+ with those sensitized by analogous dyes lacking the imine bond indicate that the latter prevents efficient electron transfer across the dye.

Solar energy conversion using first row d-block metal coordination compound sensitizers and redox mediators

“…206 An investigation of a series of heteroleptic copper(I) dyes incorporating Schiff base ancillary ligands 30-34 concluded that the presence of the imine bond prevents efficient electron transfer across the dye. 207 This can also be seen by comparing the performances of DSCs sensitized by dyes [Cu(11)(34)] + (Schiff base) and [Cu(11)(35)] + (no C]N unit). The presence of the C]N domain is detrimental to both J SC and V OC (Table 5).…”

Photoactive Copper Complexes: Properties and Applications

“…In 2020, the Constable and Housecroft groups investigated a new nonanchoring ligand design based on other electron donor moieties than those previously reported. Their first report was focused on the use of Schiff bases, with the synthesis of new bipyridine ligands bearing 4-substituted arylimines in their 4,4′-positions ( NN 280 , NN 281 , NN 282 , NN 283 , and NN 284 , entries 171–175 in Table ). These ligands did not allow any conversion enhancement, with values ranging from 0.46–1.51% due to modest J SC and V OC .…”

The Physical Chemistry and Chemical Physics (PCCP) Section of the International Journal of Molecular Sciences in Its Publications: The First 300 Thematic Articles in the First 3 Years

“…This area is the largest in terms of the number of related publications and includes 91 articles, namely [ 1 , 2 , 3 , 102 , 103 , 104 , 105 , 106 , 107 , 108 , 109 , 110 , 111 , 112 , 113 , 114 , 115 , 116 , 117 , 118 , 119 , 120 , 121 , 122 , 123 , 124 , 125 , 126 , 127 , 128 , 129 , 130 , 131 , 132 , 133 , 134 , 135 , 136 , 137 , 138 , 139 , 140 , 141 , 142 , 143 , 144 , 145 , 146 , 147 , 148 , 149 , 150 , 151 , 152 , 153 ,…”

“…The last one seems to be the most detailed, and it is precisely this that we will try to implement in the course of our narrative. As it should be expected, a priori, most of the publications in this direction are devoted to organic compounds, and primarily organic molecules; these include, with varying degrees of correctness, publications [ 1 , 2 , 3 , 102 , 103 , 104 , 106 , 108 , 112 , 117 , 118 , 119 , 121 , 124 , 127 , 128 , 130 , 131 , 132 , 133 , 135 , 138 , 139 , 140 , 141 , 142 , 143 , 144 , 146 , 147 , 148 , 151 , 153 , 154 , 156 , 157 , 164 , 165 , 166 , 168 , 171 , 172 , 174 , 176 , 178 , 180 , 183 , 185 , 186 ]. Much less space is occupied by the works related to polymeric (in fact, to a high molecular weight) compounds [ 113 , …”

“…Be that as it may, the objects in these articles are distinguished by an exceptional variety, and it is extremely difficult, if not impossible, to carry out a more detailed systematization of them (and even more so, to give details of their content in this review article). Nevertheless, in our opinion, it is worth noting here the publications devoted to Schiff’s bases, which are presented both by original research articles [ 112 , 121 , 130 , 137 , 143 , 147 , 156 , 163 ] and by two reviews; the first of which [ 125 ] presents actinide (5f-elements) complexes, and the second [ 142 ], the complexes of platinum metals. Moreover, noteworthy, are the articles, the problems of which are related to another important class of organic compounds, both theoretically and applied, namely, with various porphyrins and their derivatives [ 135 , 140 , 145 , 168 , 169 , 175 , 178 ].…”