Photochemistry and Photophysics of Coordination Compounds

More documents

Recommendations

Info

Photochemistry and Photophysics of Coordination Compounds: Copper 73 Cu(I) cluster compounds are characterized by a variety of emitting electronic levels whereas Cu(I) cationic complexes show only luminescence originating from metal-to-ligand charge-transfer (MLCT) states, as long as empty π orbitals are easily accessible in the ligands. Such MLCT transitions, which clearly take advantage of the low oxidation potential of Cu(I), arealsocommonly observed in other classes of coordination compounds, for example those of d 6 metals like Ru(II)-bipyridines [6] and Ir(III)-phenylpyridine complexes [7]. MLCT electronic transitions in coordination compounds are normally more intense when compared to MC (metal-centered) ones since they do not undergo the same prohibitions by orbital symmetry; accordingly MLCT absorption bands exhibit relatively high molar extinction coefficients. As far as emission is concerned, when MLCT excited states are the lowest-lying, they are generally characterized by long lifetimes, and potentially intense luminescence, even though exceptions are possible (vide infra). Complexes exhibiting long-lived MLCT excited states have been extensively investigated in the last decades both for a better comprehension of fundamental phenomena [8, 9] and for potential applications related to solar light harvesting and conversion [10–12]. Among them the highest attention was probably devoted to Ru(II) [13], Os(II) [14] and, more recently, Ir(III) [7] complexes, however, economical and environmental considerations make Cu(I) compounds interesting alternatives [15]. As extensively discussed in the literature, long-lived luminescent MLCT excited states of d 6 metal complexes, in particular those of Ru(II), can be strongly affected by the presence of upper lying MC levels. The latter can be partially populated through thermal activation from the MLCT states and prompt non-radiative deactivation pathways and photochemical degradation [6, 16]. Closed shell d 10 copper(I) complexes cannot suffer these kinds of problems, but undesired non-radiative deactivation channels of their MLCT levels can be favored by other factors, as will be discussed in detail further on in this review. An orbital diagram illustrating the electronic transitions of Ru(II) and Cu(I) complexes is reported in Fig. 2. 1.3 Copper in Biology Copper, even if present in traces, is an essential metal for the growth and development of biological systems. Copper plays a fundamental role in cerebral activity, nervous and cardiovascular systems, oxygen transport and cell protection against oxidation. Copper is important to strengthen the bones and to guarantee the performances of the immune system [17]. Metals are commonly found as natural constituents of proteins and, in thecourseofevolution,Naturehaslearnedhowtousethespecialproperties of metal ions to perform a wide variety of specific functions associated
74 N. Armaroli et al. Fig. 2 Qualitative comparison of orbitals and related electronic transitions in metal complexes having d 6 (e.g. Ru(II)) and d 10 (e.g. Cu(I)) configurations with life processes. It is puzzling that only a limited number of transition elements of the periodic table are utilized in biological systems, among them iron, copper, and zinc are of key importance. The criteria by which Nature chooses metals in biological systems are rather intriguing. One factor that
Page 1 and 2:
280 Topics in Current Chemistry Edi
Page 3 and 4:
Photochemistry and Photophysics of
Page 5 and 6:
Volume Editors Prof. Vincenzo Balza
Page 7 and 8:
Topics in Current Chemistry Also Av
Page 9 and 10:
X Preface nation Compounds. The ven
Page 11 and 12:
Contents Photochemistry and Photoph
Page 13 and 14:
Top Curr Chem (2007) 280: 1-36 DOI
Page 15 and 16:
Page 17 and 18:
Page 19 and 20:
Page 21 and 22:
Page 23 and 24:
Page 25 and 26:
Page 27 and 28:
Page 29 and 30:
Page 31 and 32:
Page 33 and 34: Photochemistry and Photophysics of
Page 49 and 50: Top Curr Chem (2007) 280: 37-67 DOI
Page 81 and 82: 70 N. Armaroli et al. (e.g. catenan
Page 83: 72 N. Armaroli et al. can be classi
Page 87 and 88: 76 N. Armaroli et al. Fig. 3 Theblu
Page 89 and 90: 78 N. Armaroli et al. In the CuA mi
Page 91 and 92: 80 N. Armaroli et al. pseudo-rotaxa
Page 93 and 94: 82 N. Armaroli et al. Fig. 11 Relat
Page 95 and 96: 84 N. Armaroli et al. Fig. 13 Absor
Page 97 and 98: 86 N. Armaroli et al. leading to a
Page 99 and 100: 88 N. Armaroli et al. Fig. 18 Trans
Page 101 and 102: 90 N. Armaroli et al. Fig. 20 Ligan
Page 103 and 104: 92 N. Armaroli et al. Fig. 22 Ligan
Page 105 and 106: 94 N. Armaroli et al. tionalized de
Page 107 and 108: 96 N. Armaroli et al. Fig. 24 Absor
Page 109 and 110: 98 N. Armaroli et al. prisingly, PP
Page 111 and 112: 100 N. Armaroli et al. A different
Page 113 and 114: 102 N. Armaroli et al. Cuprous clus
Page 115 and 116: 104 N. Armaroli et al. Fig. 32 Sche
Page 117 and 118: 106 N. Armaroli et al. Fig. 34 A te
Page 119 and 120: 108 N. Armaroli et al. which are va
Page 121 and 122: 110 N. Armaroli et al. Acknowledgem
Page 123 and 124: 112 N. Armaroli et al. 58. Miller M
Page 125 and 126: 114 N. Armaroli et al. 123. Armarol
Page 127 and 128: Top Curr Chem (2007) 280: 117-214 D
Page 135 and 136:
Page 137 and 138:
Page 139 and 140:
Page 141 and 142:
Page 143 and 144:
Page 145 and 146:
Page 147 and 148:
Page 149 and 150:
Page 151 and 152:
Page 153 and 154:
Page 155 and 156:
Page 157 and 158:
Page 159 and 160:
Page 161 and 162:
Page 163 and 164:
Page 165 and 166:
Page 167 and 168:
Page 169 and 170:
Page 171 and 172:
Page 173 and 174:
Page 175 and 176:
Page 177 and 178:
Page 179 and 180:
Page 181 and 182:
Page 183 and 184:
Page 185 and 186:
Page 187 and 188:
Page 189 and 190:
Page 191 and 192:
Page 193 and 194:
Page 195 and 196:
Page 197 and 198:
Page 199 and 200:
Page 201 and 202:
Page 203 and 204:
Page 205 and 206:
Page 207 and 208:
Page 209 and 210:
Page 211 and 212:
Page 213 and 214:
Page 215 and 216:
Page 217 and 218:
Page 219 and 220:
Page 221 and 222:
Page 223 and 224:
Page 225 and 226:
Top Curr Chem (2007) 280: 215-255 D
Page 227 and 228:
Page 229 and 230:
Page 231 and 232:
Page 233 and 234:
Page 235 and 236:
Page 237 and 238:
Page 239 and 240:
Page 241 and 242:
Page 243 and 244:
Page 245 and 246:
Page 247 and 248:
Page 249 and 250:
Page 251 and 252:
Page 253 and 254:
Page 255 and 256:
Page 257 and 258:
Page 259 and 260:
Page 261 and 262:
Page 263 and 264:
Page 265 and 266:
Page 267 and 268:
258 Author Index Volumes 251-280 Be
Page 269 and 270:
260 Author Index Volumes 251-280 Er
Page 271 and 272:
262 Author Index Volumes 251-280 Je
Page 273 and 274:
264 Author Index Volumes 251-280 Me
Page 275 and 276:
266 Author Index Volumes 251-280 Sa
Page 277 and 278:
268 Author Index Volumes 251-280 Vi
Page 279 and 280:
Subject Index Alkyne bridges 148 An
Page 281:
Subject Index 273 Rh(III) cyclometa
show all

Photochemistry and Photophysics of Coordination Compounds

You also want an ePaper? Increase the reach of your titles

Delete template?

Save as template?