Triazabutadiene molecules as cleavable cross-linkers adapted to cross-link components with click chemistry, e.g., clickable triazabutadienes. For example, in some embodiments, the triazabutadienes feature alkyne handles attached to the imidazole portion or the aryl portion of the triazabutadienes, wherein the alkyne handles can link to azide handles (e.g., azide handles disposed on other components) via click chemistry. Also described are methods of producing said clickable triazabutadienes and methods of use of said clickable triazabutadienes. The present invention also features methods of cleaving said clickable triazabutadienes, e.g., for liberating the diazonium species for further chemical reactions.

The invention relates to cationic direct dyes of the formula I (1), wherein m and n are independently from each other 0 or 1, D is an aromatic or a cationic heteroaromatic group, which are further specified, K is an aromatic or heteroaromatic group, E.sub.1 and E.sub.2 are independently from each other CH or N, An is an anion and a is a number from 1 to 6 and R.sub.1 and R.sub.2 are independently from each other and further specified. The compounds show washfastness at hair-dying.

##STR00001##

The near infrared absorbing curable composition includes: a compound represented by Formula (1); and a compound having a crosslinking group. In Formula (1), X.sup.1 and X.sup.2 each independently represent O, S, or a dicyanomethylene group, and A and B each independently represent a group represented by Formula (2). In Formula (2), a wave line represents a binding site of Formula (1), Y.sub.S represents a group having active hydrogen, A1 represents an aromatic hydrocarbon ring or an aromatic heterocycle, R.sub.Z represents a substituent, m1 represents an integer of 0 to mA, mA represents an integer representing the maximum number of R.sub.Z's which may be substituted in A1, Y.sub.S may be bonded to A1 or R.sub.Z to form a ring, and R.sub.Z may be bonded to A1 to form a ring.

##STR00001##

The present invention provides a luminogenic, in particular a phosphorogenic transition metal-based pyridyl complex containing a nitrone moiety, which nitrone moiety acts as a bioorthogonal functional group and an emission quencher, and can undergo cycloaddition reaction with a complementary bioorthogonal functional group coupled to a substrate. The transition metal is can be selected from iridium or ruthenium. Also disclosed is a method for preparing the transition metal-based pyridyl complex and a pharmaceutical composition comprising it. Still further provided is a method for bioorthogonal labeling of a biomolecule, a method for staining of a cell structure, a method for in vivo imaging of an organism, and a kit for in vivo imaging of an organism. The luminogenic properties and high reactivity of the complexes are highly advantageous for bioorthogonal labeling and imaging of biomolecules in their native biological environments at much lower costs than those of the existing commercial products.