inorganic chemistry

(Ben Green) #1
VISIBLE LIGHT PHOTOCATALYSIS BY METAL

HALIDE COMPLEXES CONTAINING TITANIA

AS A SEMICONDUCTOR LIGAND

HORST KISCH
Department of Chemistry and Pharmacy, Institute of Inorganic Chemistry, Friedrich-
Alexander-Universität Erlangen-Nürnbegrg, Egerlandstraße 1, Erlangen, Germany

I. Introduction 372
II. Titania–Chloroplatinum(IV) Complexes 378
A. Preparation and Characterization of Photocatalysts 379
B. Photocatalytic Degradation with Artificial
Visible Light (l455 nm) 381
C. Photodegradation with Natural Indoor and Outdoor Daylight 382
D. Mechanism 383
III. Titania–Halogenorhodium(III) Complexes (X¼Cl, Br) 384
A. Characterization 385
B. Photocatalytic Activity 387
C. Mechanism 389
IV. Summary and Outlook 391
Acknowledgments 391
References 392


ABSTRACT

Reaction of an aqueous suspension of titania with H 2 [PtCl 6 ] or
RhX 3 (X¼Cl, Br) affords halogenometalate complexes of compo-
sition {[TiO 2 ]OMXnL}z;z¼1, 2, L¼H 2 O, OH,M¼Pt: n¼4,
M¼Rh,n¼3. In these hybrid materials, titania can be viewed
as a semiconducting“inorganic ligand”bound via oxygen to a
platinum(IV) or rhodium(III) center. The quasi-Fermi level of
electrons in the titania ligand is shifted anodically by 0.2–0.3 V
as compared to the free“ligand.”In the case of the platinum com-
plex, visible light irradiation results in a platinum centered exci-
tation followed by homolytic Pt–Cl bond cleavage and electron
injection of Pt(III) into the titania conduction band. Thus, the
reducing and oxidizing surface sites can be described as a
trapped electron, that is, a Ti(III) center, and a loosely bound


371

INORGANIC PHOTOCHEMISTRY #2011 Elsevier Inc.
VOLUME 63 ISSN 0898-8838 / DOI: 10.1016/B978-0-12-385904-4.00002-0 All rights reserved

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