Even brilliant colors are all bound to scatter, Who in our changing world can stay forever? From Iroha-uta, ancient Buddhistic poem of Japan For many years we have been engaged in the preparation and characterization of new metal complexes and chelates, and especially the interpretation of their electronic spectra in solutions. In the course of these studies, we have encountered a number of strange changes in color which occur upon heating, cooling or compressing the solutions, or changing the nature of the solvent. Similar effects of temperature and pressure on the color were often also observed in the solid state. Records of visual observations, spectral measurements, and their interpretations and analyses accumulated each year, until we found ourselves, quite suddenly, in the middle of a fantastic world of color changes - the world of inorganic thermochromism and related chromo tropic phenomena. This book is a result of the reviews by Sone and Prof. S. Utsuno (Kagaku no Ryoiki, 22, 222 (1968); Bunko Kenkyu, 25,123 (1976)), and a series of papers by Fukuda, Sone et al. published in the 1. Inorg. Nucl. Chern., Bull. Chern. Soc. Japan, and various other journals after 1970.

A. Introduction

A.I Definition of "Inorganic Thermochromism" and the Aim of this Book
A.II Some Common Examples of Inorganic Thermochromism
B. Thermochromic and Chromotropic Phenomena of Cobalt(II) Chloride Solutions and Related Systems
B.I Introductory Remarks: Visual Observations on Aqueous and Alcoholic Solutions of Cobalt(II) Chloride
B.II Low-Temperature Spectrophotometric Studies on Alcoholic Solutions of Cobah(II) Chloride
B.III Effects of Water, High Pressure and Dilution on the Spectra of Alcoholic Solutions of Cobalt(II) Chloride
B.IV Thermochromic Equilibria of Cobalt(II) Chloride in Aqueous Solutions
B.V Chromotropic Phenomena of Cobalt(II) Chloride in Aprotic Solvents
B.VI Chromotropic Phenomena of Other Cobalt(II) Salts in Aqueous and Organic Solvents
B.VII Chromotropic Phenomena of Copper(II) and Nickel(II) Halides in Solution
C. Thermochromism of Nickel(II) Chelates in Solution
C.I Introduction
C.II Tetrammine-type Chelates: Octahedral-Square Planar Equilibria
C.III ß-Diketonate Chelates: Monomer-Polymer Equilibria
C.IV Mixed Diamine-ß-Diketonate Chelates: Solvatochromic and Thermochromic Equilibria Governed by the Coordinating Power (Donor Number) of the Solvent
C.V Chelates of Schiff Bases and Related Ligands: Tetrahedral-Square Planar Equilibria
C.VI Thermochromic Systems Involving Formation of Five-Coordinate Complexes and Linkage Isomerization
D. Chromotropic Phenomena of Copper(II) Chelates
D.I Introduction: Structure and Spectra of Copper(II) Chelates
D.II Acetylacetonates and Tetrammine-type Complexes
D.III Mixed Diamine-?-Diketonate Chelates
Ë. Miscellaneous Chromotropic Phenomena Observed in Solutions of Metallic Complexes
E.I Introduction
E.II Spin-Crossover in Iron(II) and Iron(III)Complexes Observed as Solution Thermochromism
E.III Iron(II) Cyanide-(Heterocyclic N-Base) Mixed Complexes: Solvatochromism Caused by Acceptor Solvents and Ions
E.IV Solvatochromism of Oxovanadium(IV) ?-Diketonates
E.V Thermochromism of Metal Chelates with Triphenylmethane Complexones in Aqueous Solutions
E. VI Thermochromism and Solvatochromism Accompanied by the Formation of Ligand Radicals in Solution
F. Thermochromism of Transition Metal Complexes in the Solid State
F.I Introduction
F.II Irreversible Thermochromism
F.III Reversible Thermochromism
F.IV Practical Applications of Solid-State Thermochromism: Color Indicators for Temperature Changes
Concluding Remarks.