[Honclbrif]

Someone in my lab just made a rhodamine derivative and all work had to halt for a few minutes while we goggled like idiots at the nuclear pink anomaly. It stands out like a lighthouse in a lab dominated by unremarkable yellows and ugly browns. Whats the most colorful thing you've made?

[Dan]

Hmmm, not so many. Off the top of my head:

1,2-bis(diphenylmethylene)hydrazine (an azine, fluorescent yellow) - this is a side product produced when protecting alcohols by heating them with diphenyldiazomethane. Fun to column out of your reaction mixture.

[nox]

The parent compound itself has a nice orange color. Dissolved in DCM, it has an intense blue-green fluorescence.

I also made a couple of polyamine linked dimers (activate COOH, couple to polyamine), and those had a beautiful dark neon green fluorescence.

[nj_bartel]

I can't get into too much detail (both due to memory and not being sure of the state of my previous group's research), but iirc, it was a three ringed aromatic structure with a phosphole as the center ring that gave a brilliant uv-active emerald color.

I also ended up with some unknown uv-active purple liquid appear in the trap to a schlenk.  Never got around to trying to figure out what it was and tossed it.

I love colors   Too unfortunate that most of my work ended in brown goop!

[azmanam]

We used the thiazolidinethione chiral auxiliary[1] for all our aldol rxns in grad school.  They are brightly crayon-yellow colored.  Make the columns a piece of cake.  Thin, dull yellow band of unreacted SM, thin (hopefully) band of undesired diastereomer, then break out the 500-mL Erlenmeyer, cuz the huge stripe of bright yellow goodness drips off the column last

See picture here:
http://www.chemistry-blog.com/2008/10/29/oh-and-what-do-you-study-in-grad-school/

Note the pink splashes on the monkey bars and variac in the picture?  That's from the reaction where I used just a touch of Rose Bengal in my reaction - only to have the bright pink reaction mixture later erupt out of the flask all over my hood.  The pink wasn't a product, but it was a really cool color to watch... until I had to clean bubble-gum pink out of every corner of my hood

[1] http://en.wikipedia.org/wiki/Aldol_reaction#Crimmins_thiazolidinethione_aldol

[fledarmus]

Ansamycin chemistry. Geldnamycin http://en.wikipedia.org/wiki/Geldanamycin is a bright yellow compound made by fermentation, and replacing the quinone methoxy with an amine gives a beautiful purple compound. Made it very easy to track by chromatography!

[opsomath]

My final project in grad school involved a para-bis(benzenediazonium) salt. Yes, that's an aryl ring with two N₂⁺ groups para to each other. No, it didn't explode...the paper should be coming out soon.

Anyway, it made lovely dark blue colors with most activated aromatics, and a really great red with dimethylaniline.

[408]

Nitrile oxides doing something f-ed turned the solution a highlighter green.

NO2 dissolved in MeCN is a nice green.  Pouring this into the organic waste turned the container bright blue.

Ozone dissolved in MeCN at -10 is a great blue.

Oxidation of a dihydro-1,2,4,5-tetrazene to the 1,2,4,5 tetrazene turns from colorless to the most intense red ever.  Tetrazenes are awesome for this.

oxidation of an amino heterocycle went via a nitroso intermediate and turned from blue to green to yellow during the reaction.

certain heterocycle N-oxides are amazingly yellow.

[nox]

My final project in grad school involved a para-bis(benzenediazonium) salt. Yes, that's an aryl ring with two N₂⁺ groups para to each other. No, it didn't explode...the paper should be coming out soon.

Anyway, it made lovely dark blue colors with most activated aromatics, and a really great red with dimethylaniline.

Be sure to provide a link when it comes out!

[408]

Nitrile oxides doing something unknown turned the solution a highlighter green.

NO2 dissolved in MeCN is a nice green.  Pouring this into the organic waste turned the container bright blue.

Ozone dissolved in MeCN at -10 is a great blue.

Oxidation of a dihydro-1,2,4,5-tetrazene to the 1,2,4,5 tetrazene turns from colorless to the most intense red ever.  Tetrazenes are awesome for this.

oxidation of an amino heterocycle went via a nitroso intermediate and turned from blue to green to yellow during the reaction.

certain heterocycle N-oxides are amazingly yellow.

[Telamond]

Most of my Pd-catalyzed reactions don't come out colorful. Maybe occassionally bright orange or yellow.

A labmate was trying to synthesize a porphyrine derivative when it broke down on the silica. Out came the colours of the rainbow separated neatly in each fraction tube. Was amazing to see it when it was coming out.

[opsomath]

Oh that is very interesting. Any speculation as to what any of the colored species might be with nitric oxide in ACN, or in the waste container?

Nitrile oxides doing something f-ed turned the solution a highlighter green.

NO2 dissolved in MeCN is a nice green.  Pouring this into the organic waste turned the container bright blue.

Ozone dissolved in MeCN at -10 is a great blue.

Oxidation of a dihydro-1,2,4,5-tetrazene to the 1,2,4,5 tetrazene turns from colorless to the most intense red ever.  Tetrazenes are awesome for this.

oxidation of an amino heterocycle went via a nitroso intermediate and turned from blue to green to yellow during the reaction.

certain heterocycle N-oxides are amazingly yellow.

[opsomath]

Y'all asked, so here it is.

http://pubs.acs.org/doi/abs/10.1021/la2024617

[Arctic-Nation]

Most of the stuff I've worked on ranged from off-white to soft yellow, but a labmate did his PhD on bodipy dyes. As these have all colours of the rainbow, and the colour persists even at ridiculously low concentrations, using common lab equipment,especially the rotavaps, after my colleague always was an adventure. Usually my stuff would turn pink.

[superg]

i once did a Corey-Fuchs reaction on an amine containing aromatic aldehyde (the first step, dibromovinyl formation): PPh3 and zinc dust in DCM is grey, after addtion of CBr4 it turns flashy green and then brown to finally give a thick grey supension after 24h. after the addition of the aldehyde, it turned bright red, then dark blue and back to red after!!!

i runned a plug filtration of the reaction mixture on silica, the red stayed stuck on top of the plug, the collected fraction were green. final purification by column gave a white compound, with the green stuck on top of the column!

never found any other so much colorfull reaction since! however for an organometallic chemist it is no uncommon to have colored compounds!!!