Chromism Research Articles

Chromic and dynamic: soft crystals of platinum(II) complexes pave the way for multi-responsive materials.

The development of smart, stimuli-responsive materials has received increased attention in the past decade for their applications as sensing technologies. This commentary discusses a timely topical review by Kato [(2024). IUCrJ, 11, 442-452] on the fabrication of multi-stimuli responsive crystals comprised of luminescent platinum(II) complexes, which exhibit intriguing chromic phenomena in response to stimuli.

Understanding of chromic phenomena: the examples of violuric acid–amino acid based salts and co-crystals

Understanding of chromic phenomena: the examples of violuric acid–amino acid based salts and co-crystals

Self-assembly of platinum(ii) 6-phenyl-2,2'-bipyridine complexes with solvato- and iono-chromic phenomena.

Mono- and di-nuclear organoplatinum(ii) monomers with cyclometalated 6-phenyl-2,2'-bipyridine ligands have been successfully constructed. These systems are capable of displaying intriguing solvato- and iono-chromic phenomena by elaborately manipulating non-covalent PtPt metal-metal and π-π stacking interactions for their self-assembly processes.

Piezochromism and hydrochromism through electron transfer: new stories for viologen materials.

While viologen derivatives have long been known for electrochromism and photochromism, here we demonstrated that a viologen-carboxylate zwitterionic molecule in the crystalline state exhibits piezochromic and hydrochromic behaviors. The yellow crystal undergoes a reversible color change to red under high pressure, to green after decompression, and finally back to yellow upon standing at ambient pressure. Ultraviolet-visible spectroscopy, X-ray photoelectron spectroscopy, electron paramagnetic resonance X-ray diffraction and DFT calculations suggested that the piezochromism is due to the formation of radicals via pressure-induced electron transfer from carboxylate to pyridinium, without a crystallographic phase transition. It was proposed that electron transfer is induced by pressure-forced reduction of intermolecular donor-acceptor contacts. The electron transfer can also be induced by dehydration, which gives a stable green anhydrous radical phase. The color change is reversible upon reabsorption of water, which triggers reverse electron transfer. The compound not only demonstrates new chromic phenomena for viologen compounds, but also represents the first example of organic mechanochromism and hydrochromism associated with radical formation via electron transfer.

Toward an Understanding of How the Optical Property of Water-Soluble Cationic Polythiophene Derivative Is Altered by the Addition of Salts: The Hofmeister Effect

Hofmeister ion-specific effects on optical properties of a water-soluble cationic polymer, poly(3-alkoxy-4-methylthiophene) (PMNT), are investigated by means of absorption, resonance Raman spectroscopy, and molecular dynamic simulations. It is found that the ionochromism of conjugated polyelectrolytes PMNT obeys Hofmeister series with high optical sensitivity, while the spectral changes result from the different electrostatic interactions and the conformational change of the cationic PMNT in different salt solutions. As a result, UV–vis absorption spectra exhibit almost no shift of absorption of PMNT in the presence of SO42–, F–, etc., whereas a red-shifted absorption of PMNT with I–, SCN– is clearly observed. To gain a deeper understanding of the nature of these anion-dependent chromic phenomena, ab initio calculations and molecular dynamics (MD) simulations are carried out to present the microscopic insights, that the Hofmeister effect occurs at the PMNT/water interface through the direct (hydrophobic, hydrophilic, and electrostatic) interactions between the anions and PMNT backbone. It is found that the salting-in anions like I– strongly suppress the hydrophobic collapse of PMNT backbone, leading to more extended and ordered PMNT backbone with red-shifted absorption, and the salting-out anions like F– strongly avoid the hydrophobic PMNT backbone, keeping a random-coiled configuration of PMNT backbone without obvious absorption changes in KF solution. The existence of ordered and disordered backbone configurations is further verified by monitoring the main in-plane skeleton Raman modes (C═C and C–C stretch) of PMNT in various salt solutions. The results presented here could provide a fundamental understanding of salt effects on chemical and biological processes occurring at the macromolecular/water interface, and then may potentially stimulate many chemical and biological applications.

Book Review: Chromic Phenomena. By Peter Bamfield.

Advanced MaterialsVolume 14, Issue 23 p. 1783-1783 Book Review Book Review: Chromic Phenomena. By Peter Bamfield. R. M. Christie, R. M. ChristieSearch for more papers by this author R. M. Christie, R. M. ChristieSearch for more papers by this author First published: 25 November 2002 https://doi.org/10.1002/1521-4095(20021203)14:23<1783::AID-ADMA1783>3.0.CO;2-QAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat No abstract is available for this article. Volume14, Issue23December, 2002Pages 1783-1783 RelatedInformation

The smart and colourful world of ‘chromic phenomena’

The smart and colourful world of ‘chromic phenomena’

Chromic phenomena in neutral polythiophene derivatives

AbstractThermochromic phenomena in various regioregular and non‐regioregular polythiophene derivatives have been investigated both in the solid state and in solution. These studies have revealed the existence of two different types of thermochromic phenomena which are correlated to the substitution pattern of the polymers. Formation of delocalized conformational defects (twistons) has been observed in regioregular polythiophene derivatives but did not occur in non‐regioregular polythiophenes. For the latter polymers, only localized conformational defects can be created along the polymer backbone leading to a monotonic blue shift of the absorption maximum upon heating. It is suggested that all these optical features are driven by order‐disorder transitions of the side‐chains, side‐chain disordering increasing their steric hindrance and/or disrupting short‐range ordered assemblies, which then force the thiophene backbone to adopt a nonplanar conformation. It has been also found that non‐covalent interactions between alkali metal ions and regioregular ether‐substituted polythiophenes can modify the side‐chain organization and can lead to interesting ionochromic effects. It is believed that chromic phenomena can be induced via a large range of external stimuli which should lead to the development of novel affinitychromic and photochromic materials.

Chromic Phenomena in Regioregular and Nonregioregular Polythiophene Derivatives

Chromic Phenomena in Regioregular and Nonregioregular Polythiophene Derivatives

Reaction Product of Tcnq with P-Phenylenedimalononitrile and the Chromic Phenomena

Abstract Complex formation of 7,7,8,8-Tetracyanoquinodimethane (TCNQ) with p-phenylenedimalononitrile (molr ratio 1:2) was assumed by DSC and IR spectral measurements. The complex shows very sensitive chromic phenomena when it contacts with moist air or with metal carbonates due to formation of TCNQ anion radical or formation of the anion radical salts.

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