Research on bimodal contrast agents in general and optical/MRI contrast agents in particular has attracted increased attention from the scientific community in recent years. Whereas optical contrast agents reveal pathologies at the cellular or sub-cellular level, MRI contrast agents generally report physiological differences at the level of tissues and organs. The complementary information obtained from these two techniques allows for a more precise diagnosis. Furthermore the emergence of near-infrared luminophores accommodates the simultaneous detection of optical and MRI signals. The current multitude and diversity in molecular architectures mirrors the ever increasing interest in the field. In this review the developments between 2010 and mid-2014 are highlighted.

Naphthalimide trifl uoroacetyl acetonate: a hydrazine-selective chemodosimetric sensorA trifl uoroacetyl acetonate naphthalimide derivative was synthesized in good yield and reacts selectively with hydrazine to give a fi ve-membered ring. This leads to OFF-ON fl uorescence with a maximum intensity at 501 nm as well as easily discernible color changes. As featured in:See Jong Seung Kim and Jonathan L. Sessler et al., Chem. Sci., 2013, 4 The trifluoroacetyl acetonate naphthalimide derivative 1 has been synthesized in good yield. In acetonitrile solution, compound 1 reacts selectively with hydrazine (NH 2 NH 2 ) to give a five-membered ring. This leads to OFF-ON fluorescence with a maximum intensity at 501 nm as well as easily discernible color changes.Based on a readily discernible and reproducible 3.9% change in overall fluorescence intensity, the limit of detection for 1 is 3.2 ppb (0.1 mM), which is below the accepted limit for hydrazine set by the U.S.Environmental Protection Agency (EPA). Compound 1 is selective for hydrazine over other amines, including NH 4 OH, NH 2 OH, ethylenediamine, methylamine, n-butylamine, piperazine, dimethylamine, triethylamine, pyridine, and is not perturbed by environmentally abundant metal ions. When supported on glass-backed silica gel TLC plates, compound 1 acts as a fluorimetric and colorimetric probe for hydrazine vapor at a partial pressure of 9.0 mm Hg, with selectivity over other potentially interfering volatile analytes, including ammonia, methylamine, n-butylamine, formaldehyde, acetaldehyde, H 2 O 2 , HCl, and CO 2 being observed. Probe 1 can also be used for the detection of hydrazine in HeLa cells and does so without appreciable interference from other biologically abundant amines and metal ions.

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Rhodamine-labelled dieckol (1) synthesized through a click reaction was found to be localized in the endoplasmic reticulum (ER) of RAW 264.7 cells. Anti-inflammatory activity of compound was considerably greater than that of dieckol itself.