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PNP-pincer-stabilized iron carbonyl dihydride complexes are key intermediates in catalytic hydrogenation and dehydrogenation reactions; however, decomposition through these intermediates has been observed. This inspires the development of a PPP-pincer system that may show improved catalyst stability. In this work, bis[2-(diisopropylphosphino)phenyl]phosphine (or

Selective and quantitative measurement of aqueous nitrate (NO3−) anion is achieved using solid [Pt(Cl-4-tpy)Cl]ClO4 salt (Cl-4-tpy = 4-chloro-2,2′:6′2′′-terpyridine), and as the salt supported on controlled porous glass.

15aneN5 is structurally characterized complexed to Cr3+, Mn3+, Fe3+, Co3+, and Cu2+ for the first time. Ru3+ complexation yields a Ru2+ diimine structure. A geometric factor quantifies the coordination geometry of the ligand in its complexes.

Iron dihydride complexes are key intermediates in many iron-catalyzed reactions. Previous efforts to study molecules of this type have led to the discovery of a remarkably stable

Iron hydrides supported by a pincer ligand of the type HN(CH2CH2PR2)2 (RPNHP) are versatile hydrogenation catalysts. Previous efforts have focused on using CO as an additional ligand to stabilize the hydride species. In this work, CO is replaced with isocyanide ligands, leading to the isolation of two different types of iron hydride complexes: (RPNHP)FeH(CNR')(BH4) (R = iPr, R' = 2,6-Me2C6H3, tBu; R = Cy, R' = 2,6-Me2C6H3) and [(iPrPNHP)FeH(CNtBu)2]X (X = BPh4, Br, or a mixture of Br and BH4). The neutral iron hydrides are capable of catalyzing the hydrogenation of PhCO2CH2Ph to PhCH2OH, although the activity is lower than for (iPrPNHP)FeH(CO)(BH4). The cationic iron hydrides are active hydrogenation catalysts only for more reactive carbonyl substrates such as PhCHO, and only when the NH and FeH hydrogens are syn to each other. The cationic species and their synthetic precursors [(iPrPNHP)FeBr(CNtBu)2]X (X = BPh4, Br) can have different configurations for the isocyanide ligands (cis or trans) and the H-N-Fe-H(Br) unit (syn or anti). Unlike tetraphenylborate, the bromide counterion participates in a hydrogen-bonding interaction with the NH group, which influences the relative stability of the cis,anti and cis,syn isomers. These structural differences have been elucidated by X-ray crystallography, and the geometric isomerization processes have been studied by NMR spectroscopy.

The reaction of 1,3,5-(iPr2PO)3C6H3 with Co2(CO)8 leads to the isolation of a POCOP-type mononuclear pincer complex {κP,κC,κP-2,4,6-(iPr2PO)3C6H2}Co(CO)2 (1) or a tetranuclear species {κP-{κP,κC,κP-2,4,6-(iPr2PO)3C6H2}Co(CO)2}2Co2(CO)6 (2), depending on the ligand to cobalt ratio employed. The latter compound can be an impurity during the synthesis of {2,6-(iPr2PO)2-4-Me2N-C6H2}Co(CO)2, when the ligand precursor 5-(dimethylamino)resorcinol is contaminated with phloroglucinol due to incomplete monoamination. Similarly, the reaction of 1,3,5-(iPr2PO)3C6H3 with NiCl2 in the presence of 4-dimethylaminopyridine provides {κP,κC,κP-2,4,6-(iPr2PO)3C6H2}NiCl (3) bearing an appended phosphinite group. Structures 1–3 have been studied by X-ray crystallography.

HN(CH2CH2PR2)2-ligated copper borohydride complexes, (RPNHP)Cu(BH4) (R = iPr, Cy, tBu), which can be prepared from (RPNHP)CuBr and NaBH4, are capable of catalyzing the hydrogenation of aldehydes in an alcoholic solvent. More active hydrogenation catalysts are (RPNHP)CuBr mixed with KOtBu, allowing various aldehydes and ketones to be efficiently reduced to alcohols except those bearing a nitro, N-unprotected pyrrole, pyridine, or an ester group, or those prone to aldol condensation (e.g., 1-heptanal). Modifying the catalyst structure by replacing the NH group in (iPrPNHP)CuBr with an NMe group results in an inferior catalyst but preserves some catalytic activity. The hexanuclear copper hydride cluster, (iPrPNHP)3Cu6H6, is also competent in catalyzing the hydrogenation of aldehydes such as benzaldehyde and N-methyl-2-pyrrolecarboxaldehyde, albeit accompanied by decomposition pathways. The catalytic performance can be enhanced through the addition of a strong base or iPrPNHP. The three catalytic systems likely share the same catalytically active species, which is proposed to be a mononuclear copper hydride (RPNHP)CuH with the NH group bound to copper.

An efficient and versatile method for the synthesis of 1,4-diaryl tetrazolones 1 is reported which involves C–N coupling of aryl tetrazolones 2 with aryl boronic acids 3 in the presence of Cu2O nanoparticles under an oxygen atmosphere and DMSO as solvent. The reaction tolerates a variety of electron donating and electron withdrawing substituents on both substrates and produces the desired 1,4-diaryl tetrazolones 1 in moderate to good yields. In the crystal lattice, the molecules exhibit π⋯π stacking interactions between the adjacent layers as well as weak through-space electrostatic C–H⋯O interactions involving the pendant rings and tetrazolone carbonyl. 1-(4-Methoxyphenyl)-4-(3-tolyl)-1,4-dihydro-5H-tetrazol-5-one 1bk and 1-(3-fluorophenyl)-4-(4-methoxyphenyl)-1,4-dihydro-5H-tetrazol-5-one 1be, differing only in the presence of one group (methyl or fluoro), exhibited an identical pattern of noncovalent interactions in the solid-state. Hirshfeld surface analyses have also been performed to visualize intermolecular interactions.

Inorganic Chemistry teaches students the concept that modifications to ligand structures, especially the donor properties, can have a drastic impact on the reactivity and stability of the metal complexes. Experiments described here reinforce this concept through the investigation of two tetradentate ligands derived from o-phenylenediamine and salicylaldehyde. The Schiff base ligand, H2salophen, reacts with Ni(OAc)2·4H2O to yield a maroon, square planar complex, Ni(salophen). Under the same conditions, the amine-type ligand, H2salophan, forms a light-blue compound analyzed as [Ni(Hsalophan)(OAc)]2. The Ni(salophan) complex free of acetate may be produced from the reaction of H2salophan with Ni(OAc)2·4H2O in the presence of NaOH but undergoes ligand dehydrogenation to yield Ni(salophen). Students conducting these experiments have the opportunity to learn synthetic techniques and various characterization methods. Most importantly, the inquiry-guided experimental design helps them develop critical thinking skills and apply acquired knowledge to solving a research problem in a laboratory course.

Cobalt POCOP pincer complexes {κP,κC,κP-2,6-(iPr2PO)2C6H3}Co(PMe3)2 (1) and {κP,κC,κP-2,6-(iPr2PO)2-4-NMe2-C6H2}Co(PMe3)2 (2) have been synthesized via C–H bond activation of the pincer ligands wit...

When exposed to UV light, single crystals of the vinyl azides 3-azido-1-phenylpropenone (1a), 3-azido-1-(4-methoxyphenyl)propenone (1b), and 3-azido-1-(4-chlorophenyl)propenone (1c) exhibit dramatic mechanical effects by cracking or bending with the release of N2. Mechanistic studies using laser flash photolysis, supported by quantum mechanical calculations, show that each of the vinyl azides degrades through a vinylnitrene intermediate. However, despite having very similar crystal packing motifs, the three compounds exhibit distinct photomechanical responses in bulk crystals. While the crystals of 1a delaminate and release gaseous N2 indiscriminately under paraffin oil, the crystals of 1b and 1c visibly expand, bend, and fracture, mainly along specific crystallographic faces, before releasing N2. The photochemical analysis suggests that the observed expansion is due to internal pressure exerted by the gaseous product in the crystal lattices of these materials. Lattice energy calculations, supported by nanoindentation experiments, show significant differences in the respective lattice energies. The calculations identify critical features in the crystal structures of 1b and 1c where elastic energy accumulates during gas release, which correspond to the direction of the observed cracks. This study highlights the hitherto untapped potential of photochemical gas release to elicit a photomechanical response and motility of photoreactive molecular crystals.

Copper hydride clusters of the type (RPNHP)nCu2nH2n (RPNHP = HN(CH2CH2PR2)2; n = 2 and 3) have been synthesized from the reaction of (RPNHP)CuBr with KOtBu under H2 or in one pot from a 1:2:2 mixture of RPNHP, CuBr, and KOtBu under H2. With medium-sized phosphorus substituents (R = iPr and Cy), the phosphine ligands stabilize both hexanuclear and tetranuclear clusters; however, the smaller clusters are kinetic products and aggregate further over time. Use of a bulkier ligand tBuPNHP leads to the formation of only a tetranuclear cluster. Crystallographic studies reveal a distorted octahedral Cu6 unit in (iPrPNHP)3Cu6H6 (2a) and (CyPNHP)3Cu6H6 (2b), while a tetrahedral Cu4 unit exists in (CyPNHP)2Cu4H4 (2b') and (tBuPNHP)2Cu4H4 (2c'), all furnished with face-capping hydrides and bridging RPNHP ligands. The aggregations are maintained in solution, although hydrides are fluxional. These copper clusters are capable of reducing aldehydes and ketones to the corresponding copper alkoxide species. Ranking their reactivity toward N-methyl-2-pyrrolecarboxaldehyde gives 2b' > 2a, 2b ≫ 2c', which correlates inversely with the order of thermal stability (against decomposition and cluster expansion).

To clarify the cis-trans isomerization mechanism of simple alkenes on the triplet excited state surface, the photochemistry of acyclic and cyclic vinyl ketones with a p-methoxyacetophenone moiety as a built-in triplet sensitizer (1 and 2, respectively) was compared. When irradiated, ketone 1 produces its cis-isomer, whereas ketone 2 does not yield any photoproducts. Laser flash photolysis of ketone 1 yields a transient spectrum with λmax ∼ 400 nm (τ ∼ 125 ns). This transient is assigned to the first triplet excited state (T1) of 1, which presumably decays to form a triplet biradical (1BR) that is shorter lived than the triplet ketone. In comparison, laser flash photolysis of 2 reveals two transients (τ ∼ 20 and 440 ns), which are assigned to T1 of 2 and triplet biradical 2BR, respectively. Density functional theory calculations support the characterization of the triplet excited states and the biradical intermediates formed upon irradiation of ketones 1 and 2 and allow a comparison of the physical properties of the biradical intermediates. As the biradical centers in 2BR are stabilized by conjugation, 2BR is more rigid than 1BR. Therefore, the longer lifetime of 2BR can be attributed to less-efficient intersystem crossing to the ground state.

Rigid and topologically constrained ethylene cross-bridged tetraazamacrocycles have been increasingly utilised for thirty years as they form remarkably stable transition metal complexes for catalysis, biomedical imaging, and inorganic drug molecule applications. Extending these benefits to pentaazamacrocycles has been achieved and a first transition metal complex prepared and structurally characterized.

Solvent plays a vital role in the recrystallization process and resulting crystallinity of materials. This role is of such importance that it can control the stability and utility of materials. In this work, the inclusion of a solvent in the crystalline lattice, specifically water, drastically affects the overall stability of two platinum polymorphs. [Pt(tpy)Cl]BF4 (tpy = 2,2';6'2″-terpyridine) crystallizes in three forms, red (1R) and blue (1B) polymorphs and a yellow nonsolvated form (2). 1R is the more stable of the two polymorphs, whereas 1B loses crystallinity upon dehydration at ambient conditions resulting in the formation of 2. Close examination of the solid-state extended structures of the two polymorphs reveals that 1R has a lattice arrangement that is more conducive to stronger intermolecular interactions compared to 1B, thereby promoting greater stability. In addition, these two polymorphs exhibit unique vapochromic responses when exposed to various solvents.

PtI2(5,5'-bis(HCF2CH2OCH2)-2,2'-bpy)], 55-2FH-PtI2, is the first example of a substituted fluorinated diiodoplatinum diimine complex that exhibits polymorphism. The complex, upon recrystallization, forms two different polymorphs, denoted as α and β forms. The luminescence of the α and β forms are the same in glassy solution at 77 K; however, in the solid state, they differ significantly. The major difference between them lies in the solid-state packing of the crystalline structure. The α form is a square planar polyfluorinated PtI2-containing complex. Its extended herringbone structure consists of two neighboring stacked bipyridyl planes that do not overlap. The α form emits stronger than its parent molecule, [PtI2bpy], and much stronger than the β polymorph. The β form has a slight tetrahedral distortion about the metal center that ultimately changes the geometry of the complex and decreases the d-orbital splitting from square planar. Furthermore, overlapping bipyridine rings in the extended structure of the β form quench the emission thus resulting in a lower energy emission. Additionally, the β form shows only one type of C-H···O intermolecular stacking interaction that can cause the moderate distortion of the metal core.

A total of 44 bis-aryl-monocyclic polyamines, monoaryl-monocyclic polyamines and their transition metal complexes were prepared, chemically characterized, and screened in vitro against the Leishmania donovani promastigotes, axenic amastigotes and intracellular amastigotes in THP1 cells. The IC(50) and/or IC(90) values showed that 10 compounds were similarly active at about 2-fold less potent than known drug pentamidine against promastigotes. The most potent compound had an IC(50) of 2.82 μM (compared to 2.93 μM for pentamidine). Nine compounds were 1.1–13.6-fold more potent than pentamidine against axenic amastigotes, the most potent one being about 2-fold less potent than amphotericin B. Fourteen compounds were about 2–10 fold more potent than pentamidine, the most potent one is about 2-fold less potent than amphotericin B against intracellular amastigotes in THP1 cells. The 2 most promising compounds (FeL7Cl(2) and MnL7Cl(2)), with strong activity against both promastigotes and amastigotes and no observable toxicity against the THP1 cells are the Fe(2+)- and Mn(2+)- complexes of a dibenzyl cyclen derivative. Only 2 of the 44 compounds showed observable cytotoxicity against THP1 cells. Tetraazamacrocyclic monocyclic polyamines represent a new class of antileishmanial lead structures that warrant follow up studies.

A nickel hydride complex, {2,6-(iPr2PO)2C6H3}NiH, has been shown to catalyze the coupling of RCHO and R′OH to yield RCO2R′ and RCH2OH, where the aldehyde also acts as a hydrogen acceptor and the alcohol also serves as the solvent. Functional groups tolerated by this catalytic system include CF3, NO2, Cl, Br, NHCOMe, and NMe2, whereas phenol-containing compounds are not viable substrates or solvents. The dehydrogenative coupling reaction can alternatively be catalyzed by an air-stable nickel chloride complex, {2,6-(iPr2PO)2C6H3}NiCl, in conjunction with NaOMe. Acids in unpurified aldehydes react with the hydride to form nickel carboxylate complexes, which are catalytically inactive. Water, if present in a significant quantity, decreases the catalytic efficiency by forming {2,6-(iPr2PO)2C6H3}NiOH, which causes catalyst degradation. On the other hand, in the presence of a drying agent, {2,6-(iPr2PO)2C6H3}NiOH generated in situ from {2,6-(iPr2PO)2C6H3}NiCl and NaOH can be converted to an alkoxide species, bec...

Organic molecules that contain alkyl-difluoromethyl moieties have received increased attention in medicinal chemistry, but their synthesis in a modular and late-stage fashion remains challenging. We report herein an efficient copper-catalyzed radical relay approach for the carbo-difluoromethylation of alkenes. This approach simultaneously introduces CF2H groups along with complex alkyl or aryl groups into alkenes with regioselectivity opposite to traditional CF2H radical addition. We demonstrate a broad substrate scope and a wide functional group compatibility. This scalable protocol is applied to the late-stage functionalization of complex molecules and the synthesis of CF2H analogues of bioactive molecules. Mechanistic studies and density functional theory calculations suggest a unique ligand effect on the reactivity of the Cu-CF2H species., Compounds that contain alkyl-difluoromethyl moieties are of interest for medicinal chemistry, but their synthesis is challenging. Here, the authors report a copper-catalyzed radical relay approach for the carbodifluoromethylation of alkenes that simultaneously introduces CF2H groups and complex alkyl or aryl groups into alkenes.

Iron hydrides supported by a pincer ligand of the type HN(CH

Increased levels of nitrate (NO3-) in the environment can be detrimental to human health. Herein, we report a robust, cost-effective, and scalable, hybrid material-based colorimetric/luminescent sensor technology for rapid, selective, sensitive, and interference-free in situ NO3- detection. These hybrid materials are based on a square-planar platinum(II) salt [Pt(tpy)Cl]PF6 (tpy = 2,2';6',2″-terpyridine) supported on mesoporous silica. The platinum salt undergoes a vivid change in color and luminescence upon exposure to aqueous NO3- anions at pH ≤ 0 caused by substitution of the PF6- anions by aqueous NO3-. This change in photophysics of the platinum salt is induced by a rearrangement of its crystal lattice that leads to an extended Pt···Pt···Pt interaction, along with a concomitant change in its electronic structure. Furthermore, incorporating the material into mesoporous silica enhances the surface area and increases the detection sensitivity. A NO3- detection limit of 0.05 mM (3.1 ppm) is achieved, which is sufficiently lower than the ambient water quality limit of 0.16 mM (10 ppm) set by the United States Environmental Protection Agency. The colorimetric/luminescence of the hybrid material is highly selective to aqueous NO3- anions in the presence of other interfering anions, suggesting that this material is a promising candidate for the rapid NO3- detection and quantification in practical samples without separation, concentration, or other pretreatment steps.

Tricarbonylrhenium(I)(α-diimine) complexes are of importance because of their strong cytotoxic and fluorescence properties. Syntheses of such complexes were achieved through a two-step process. First, the pentylcarbonato complexes, fac-(CO)(3)(α-diimine)ReOC(O)OC(5)H(11) were synthesized through a microwave-assisted reaction of Re(2)(CO)(10), α-diimine, 1-pentanol and CO(2) in a few hours. Second, the pentylcarbonato complexes are treated with carboxylic, sulfonic and halo acids to obtain the corresponding carboxylato, sulfonato and halido complexes. This is the first example of conversion of Re(2)(CO)(10) into a rhenium carbonyl complex through microwave-assisted reaction.

When exposed to UV light, single crystals of the vinyl azides 3-azido-1-phenylpropenone (

Inorganic Chemistry teaches students the concept that modifications to ligand structures, especially the donor properties, can have a drastic impact on the reactivity and stability of the metal complexes. Experiments described here reinforce this concept through the investigation of two tetradentate ligands derived from o-phenylenediamine and salicylaldehyde. The Schiff base ligand, H2salophen, reacts with Ni(OAc)2•4H2O to yield a maroon colored, square planar complex, Ni(salophen). Under the same conditions, the amine-type ligand, H2salophan, forms a light-blue compound with a formula Ni(salophan)(HOAc). Complex Ni(salophan) free of acetate may be produced from the reaction of H2salophan with Ni(OAc)2•4H2O in the presence of NaOH, but undergoes ligand dehydrogenation to yield Ni(salophen). Students conducting these experiments have the opportunity to learn synthetic techniques and various characterization methods. Most importantly, the inquiry-guided experimental design helps them develop critical thinking skills and apply acquired knowledge to solving a research problem in a laboratory course.

Copper hydride clusters of the type (

Red crystals of [Pt(tpy)Cl]NO3·HNO3 show mechanochromic behaviour turning yellow when pressure is applied. The electronic character and spectroscopic signature of the red and yellow polymorphs change as a result of slipping of the molecular stacking planes in the solid state. The slippage alters the PtPt intermolecular distances from a linear stacked motif with

Rigid and topologically constrained ethylene cross-bridged tetraazamacrocycles have been increasingly utilised for thirty years as they form remarkably stable transition metal complexes for catalysis, biomedical imaging, and inorganic drug molecule applications. Extending these benefits to pentaazamacrocycles has been achieved and a first transition metal complex prepared and structurally characterized.

A phosphinite-based dinickel pincer complex, {2,3,5,6-(iPr2PO)4C6}Ni2Cl2, is synthesized by heating a mixture of 1,2,4,5-tetrahydroxybenzene, iPr2PCl, NiCl2, and Et3N at 150 °C in a microwave reactor or refluxing 1,2,4,5-(iPr2PO)4C6H2 with NiCl2 and Et3N at 175–250 °C in a flask. Substitution of chlorides by hydrides (from LiAlH4 or LiEt3BH) and methyl groups (from MeLi) generates {2,3,5,6-(iPr2PO)4C6}Ni2H2 and {2,3,5,6-(iPr2PO)4C6}Ni2Me2, respectively. Protonation of the methyl complex with HCO2H gives {2,3,5,6-(iPr2PO)4C6}Ni2(OCHO)2. Spectroscopic and crystallographic data of these Janus POCOP pincer complexes are compared to those of the analogous mononuclear complexes {2,6-(iPr2PO)2C6H3}NiX (X = Cl, H, Me, and OCHO). The hydride complex {2,3,5,6-(iPr2PO)4C6}Ni2H2 reacts with phenylacetylene and CO2 to give insertion products. It also catalyzes the reduction of CO2 with catecholborane (HBcat) to yield CH3OBcat and catBOBcat with a turnover frequency of 7.5 min–1. The stoichiometric and catalytic activi...

A series of cobalt POCOP pincer complexes with the formulas {2,6-(iPr2PO)2-4-R′-C6H2}Co(CO)2 (R′ = H (1a), NMe2 (1b), OMe (1c), CO2Me (1d)), {2,6-(Ph2PO)2C6H3}Co(CO)2 (1e), and {2,6-(tBu2PO)2C6H3}Co(CO) (2f) have been synthesized through C–H bond activation of the corresponding pincer ligands with Co2(CO)8. These complexes have been demonstrated to catalyze the hydrosilylation of PhCHO with (EtO)3SiH, which exhibits an induction period and the decreasing reactivity order 1b > 1c > 1a > 1d > 1e. The catalytic protocol can be applied to various aldehydes with turnover numbers of up to 300. The CO ligands in the dicarbonyl complexes have been shown to exchange with 13CO at room temperature and partially dissociate from cobalt at high temperatures. Substitution of CO by tert-butyl isocyanide has been accomplished with 1a at 50–80 °C, resulting in the formation of {2,6-(iPr2PO)2C6H3}Co(CNtBu)(CO) (3a) and {2,6-(iPr2PO)2C6H3}Co(CNtBu)2 (4a). The catalytic reactions are more efficient when they are carried out i...

Cisplatin and other metal-based drugs often display side effects and tumor resistance after prolonged use. Because rhenium-based anticancer complexes are often less toxic, a novel series of organorhenium complexes were synthesized of the types: XRe(CO)(3)Z (X = α-diimines and Z = p-toluenesulfonate, 1-naphthalenesulfonate, 2-naphthalenesulfonate, picolinate, nicotinate, aspirinate, naproxenate, flufenamate, ibuprofenate, mefenamate, tolfenamate, N-acetyl-tryptophanate), and their biological properties were examined. Specifically, in hormone-dependent MCF-7 and hormone-independent triple-negative MDA-MB-231 breast cancer cells, the p-toluenesulfonato, 1-naphthalenesulfonato, 2-naphthalenesulfonato, picolinato, nicotinato, acetylsalicylato, flufenamato, ibuprofenato, mefenamato, and N-acetyl-tryptophanato complexes were found to be far more potent than conventional drug cisplatin. DNA-binding studies were performed in each case via UV–Vis titrations, cyclic voltammetry, gel electrophoresis, and viscosity, which suggest DNA partial intercalation interaction, and the structure–activity relationship studies suggest that the anticancer activities increase with the increasing lipophilicities of the compounds, roughly consistent with their DNA-binding activities.

POCOP-pincer ligated palladium hydrocarbyl complexes [2,6-(R2PO)2C6H3]PdR′ have been prepared from the reaction between [2,6-(R2PO)2C6H3]PdCl and R'Li. X-ray crystallographic studies of these complexes show that the Pd–R′ bond becomes shorter when the metal-bound carbon has more s character. Comparing the relative reactivity of these palladium hydrocarbyl (including hydride) complexes toward phenylacetylene suggests that the rate of the C–H exchange process follows a decreasing order of Pd–H > Pd–Csp3 > Pd–Csp2 > Pd–Csp. The palladium phenyl complex [2,6-(R2PO)2C6H3]PdPh is exceptionally slow for the reaction with phenylacetylene, possibly due to a high-energy conformer required for the palladium-carbon bond cleavage.

Irradiation of nanocrystals of azide 1 results in a solid-to-solid reaction that forms imine 2 in high chemical yield. In contrast, solution photolysis of azide 1 yields a mixture of products, with 7 as the major one. Laser flash photolysis (LFP) of a nanocrystalline suspension of azide 1 in water shows selective formation of benzoyl radical 4 (λmax ∼ 400 nm), which is short-lived (τ = 833 ns) as it intersystem crosses to form imine 2. In comparison, LFP of azide 1 in methanol reveals the formation of triplet alkylnitrene 10 (λmax ∼ 340 nm). The selectivity observed in the solid-state is related to stabilization of the triplet ketone with (n,π*) configuration by the crystal lattice, which results in α-cleavage being favored over triplet energy transfer to the azido chromophore. Both the solid-state and solution reaction mechanisms are further supported by density functional theory calculations. Thus, laser flash photolysis has been used to effectively elucidate the medium dependent reaction mechanisms of azide 1.