Ena Luis

All Publications

• Hierarchical lanthanide-based self-assembly complexes that undergo reversible luminescent response to both temperature changes and chemical reactions within competitive media DALTON TRANSACTIONS Gorai, T., Lovitt, J. I., Twamley, B., Luis, E. T., Gunnlaugsson, T. 2025; 54 (25): 10022-10029

  Abstract

  Here, we report hierarchical self-assembly formation of a luminescent Eu3+-1-DPA complex in mixed aqueous-organic (THF or ethanol) solutions. Its reversible responsive behaviour to temperature change and in situ chemical reactions were investigated. The ligands 1-DPA and 1-DPA-acetate as well as the Eu(III) complex of 1-DPA, Eu3+-1-DPA were synthesised, and their X-ray crystal structures were determined. The photophysical and material (morphological) properties of the ligands and Eu(III) complexes formed in situ of both 1-DPA and 1-DPA-acetate were probed in mixed aqueous-organic (THF or ethanol) solutions. The ligands as well as the complexes were shown to aggregate into hierarchical and homogenously formed microspheres and microrods, as demonstrated by carrying out SEM of the drop-cast solutions of these complexes in ethanol-water mixtures. The Eu3+-1-DPA complex gave rise to Eu(III)-centred emission [due to deactivation of the 5D0 → 7FJ (J = 1-4)]. It showed reversible, thermo-responsive lanthanide-centred emission, while in situ esterification using acidic anhydride (forming Eu3+-1-DPA-acetate, which was not emissive), and the subsequent NaOH-mediated hydrolysis of the Eu3+-1-DPA-acetate assembly induced both Eu(III)-emission and morphological changes, as demonstrated using both spectroscopic and SEM studies.

  View details for DOI 10.1039/d5dt00831j

  View details for Web of Science ID 001502949100001

  View details for PubMedID 40476331

• Emissive triphenylamine functionalised 1,8-naphthalimide and naphthalene diimide fluorophores: aggregation, computation and biological studies JOURNAL OF MATERIALS CHEMISTRY B Ramirez Lazaro, L., Sigurvinsson, L., Curtin, N., Ho, J., Luis, E. T., Mcadams, D. A., Gudmundsson, T. A., Hawes, C. S., Jacquemin, D., O'Shea, D. F., Scanlan, E. M., Gunnlaugsson, T., Henwood, A. F. 2025; 13 (3): 929-942

  Abstract

  Four new aromatic imides bearing triphenylamino (TPA) moieties are reported each of which differ by the number and/or positional arrangements of the TPA units. Compounds 1-3 are 1,8-naphthalimides (naps) that contain N,N'-diphenyl-[1,1'-biphenyl]-4-amino (TPA-Ph) groups appended to the N-termini of the respective imides. Each differs by their functionalisation of the 4-position of the nap: nitro (1), amino (2), or an additional TPA group (3). By contrast, compound 4 is a naphthalene diimide (NDI) functionalised with TPA-Ph moieties on each N-terminus. These simple modifications produce molecules with vastly different optoelectronic and aggregation properties. This article studies these characteristics with particular focus directed toward the contrast in aggregation-caused quenching (ACQ) properties of 2 compared with the aggregation-induced emission (AIE) properties of 3. The distinct aggregation and photophysical properties of 2 and 3 are delicately exploited using self-assembly with an amphiphilic poloxamer to generate nanoparticles capable of delivering 2 and 3 into cells for biological imaging.

  View details for DOI 10.1039/d4tb01905a

  View details for Web of Science ID 001370079100001

  View details for PubMedID 39635833

• Mechanistic and Kinetic Insights into Intermolecular [2+2] Photocycloadditions ACS CATALYSIS Quach, G., Iranmanesh, H., Luis, E. T., Harper, J. B., Beves, J. E., Moore, E. G. 2024; 14 (11): 8758-8766

  View details for DOI 10.1021/acscatal.4c01678

  View details for Web of Science ID 001242560400001

• The kinetics and mechanism of interconversion within a system of [Fe₂₃]<SUP>4+</SUP> helicates and [Fe₄₆]<SUP>8+</SUP> cages CHEMICAL COMMUNICATIONS Siddique, R. G., Arachchige, K. S. A., AL-Fayaad, H. A., Brock, A. J., Micallef, A. S., Luis, E. T., Thoburn, J. D., McMurtrie, J. C., Clegg, J. K. 2021; 57 (40): 4918-4921

  Abstract

  Nature builds simple molecules into highly complex assemblies, which are involved in all fundamental processes of life. Some of the most intriguing biological assemblies are those that can be precisely reconfigured to achieve different functions using the same building blocks. Understanding the reconfiguration of synthetic self-assembled systems will allow us to better understand the complexity of proteins and design useful artificial chemical systems. Here we have prepared a relatively simple system in which two distinct self-assembled structures, a [Fe2L3]4+ helicate and a [Fe4L6]8+ cage that are formed from the same precursors, coexist at equilibrium. We have measured the rates of interconversion of these two species and propose a mechanism for the transformation.

  View details for DOI 10.1039/d1cc01583d

  View details for Web of Science ID 000641056700001

  View details for PubMedID 33870998

• Hydrazone exchange: a viable route for the solid-tethered synthesis of [2]rotaxanes NEW JOURNAL OF CHEMISTRY Da Silva Rodrigues, R., Luis, E. T., Marshall, D. L., McMurtrie, J. C., Mullen, K. M. 2021; 45 (9): 4414-4421

  View details for DOI 10.1039/d1nj00388g

  View details for Web of Science ID 000626241900033

• Stepwise reduction of interlocked viologen-based complexes in the gas phase CHEMICAL COMMUNICATIONS Marshall, D. L., Poad, B. L. J., Luis, E. T., Rodrigues, R., Blanksby, S. J., Mullen, K. M. 2020; 56 (88): 13575-13578

  Abstract

  We present the first application of electrochemical reduction in an ion trap mass spectrometer as a dual-function tool to synthesise and probe the reactivity of interlocked viologen-based complexes. Compared with non-complexed archetypes, electron-donating macrocyclic porphyrin ethers retard electron transfer reaction rates and stabilise intact structures in low oxidation states.

  View details for DOI 10.1039/d0cc05115b

  View details for Web of Science ID 000585555100014

  View details for PubMedID 33052365

• Photophysical Activity and Host-Guest Behavior of Ruthenium Polypyridyl Catalysts Encapsulated in Cucurbit[10]uril INORGANIC CHEMISTRY Luis, E. T., Day, A., Koenig, B., Beves, J. E. 2020; 59 (13): 9135-9142

  Abstract

  This work outlines a strategy to combine the use of visible light and confined spaces to form a supramolecular photocatalyst system. Polypyridyl ruthenium(II) complexes [Ru(bpy)3]2+ (bpy = 2,2'-bipyridine), [Ru(bpy)2(bpm)]2+ (bpm = 2,2'-bipyrimidine), and [Ru(bpy)2(bpz)]2+ (bpz = 2,2'-bipyrazine) are encapsulated in cucurbit[10]uril to form host-guest systems in aqueous solution. The photophysical properties of the complexes are altered by encapsulation, with improved emissive behavior for the heteroleptic complexes. Oxidative quenching of the photocatalyst's excited state via intermolecular charge transfer to methyl viologen can occur within the internal cavity, which acts to preorganize the reagents. The host-guest system containing [Ru(bpy)3]2+ can bind suitable substrates, and essential criteria for its use as a supramolecular photocatalyst are investigated.

  View details for DOI 10.1021/acs.inorgchem.0c00986

  View details for Web of Science ID 000548456300052

  View details for PubMedID 32578987

• The p<i>K</i>_a values of <i>N</i>-aryl imidazolinium salts, their higher homologues, and formamidinium salts in dimethyl sulfoxide ORGANIC & BIOMOLECULAR CHEMISTRY Konstandaras, N., Dunn, M. H., Luis, E. T., Cole, M. L., Harper, J. B. 2020; 18 (10): 1910-1917

  Abstract

  A series of imidazolinium salts, their six-, seven- and eight-membered homologues, and the related formamidinium salts were prepared, and their pKa values were determined in DMSO at 25 °C using the bracketing indicator method. The effect of each type of structural variation on the acidity of each salt was considered, particularly noting the importance of ring size and the effect of the steric and electronic nature of the N-aryl substituents. The effect of a cyclic structure was also probed through comparing the cyclic systems with the corresponding formamidinium salts, noting the importance of conformational flexibility in the latter cases. Along with allowing choice of appropriate bases for deprotonation of these species, it is anticipated that the data presented will aid in the understanding of the nucleophilicity, and potentially catalytic efficacy, of the corresponding carbenes.

  View details for DOI 10.1039/d0ob00036a

  View details for Web of Science ID 000519640500007

  View details for PubMedID 32095802

• Diastereoselective Control of Tetraphenylethene Reactivity by Metal Template Self-Assembly CHEMISTRY-A EUROPEAN JOURNAL Kennedy, A. D. W., de Haas, N., Iranmanesh, H., Luis, E. T., Shen, C., Wang, P., Price, J. R., Donald, W. A., Andreasson, J., Huang, F., Beves, J. E. 2019; 25 (22): 5708-5718

  Abstract

  The reaction of 4,4',4'',4'''-(ethene-1,1,2,2-tetrayl)tetraaniline with 2-pyridinecarboxaldehyde and iron(II) chloride resulted, after aqueous workup, in the diastereoselective formation of an [Fe2 L3 ]4+ triple-stranded helicate structure, irrespective of the stoichiometry employed. The helicate structure was characterized in solution by multinuclear NMR spectroscopy, and in the solid state by single-crystal X-ray crystallography. The reaction of iron(II) tetrafluoroborate or iron(II) bistriflimide with the tetraaniline and 2-pyridinecarboxaldehyde allowed the formation of an [Fe8 L6 ]16+ cube when the appropriate stoichiometry was used, but these structures were unstable with respect to hydrolysis. The pendant amine groups on the helicate can be functionalized by reaction with acid chlorides or anhydrides, and the resulting functionalized tetraphenylethene (TPE) units were isolated by the reaction of the helicate with tris(2-aminoethyl)amine. The emission properties of the TPE units were studied in THF/water mixtures, and they were found by dynamic light scattering to self-assemble into large (av. diameter 250 nm) structures.

  View details for DOI 10.1002/chem.201806259

  View details for Web of Science ID 000467079100015

  View details for PubMedID 30775812

• Photosubstitution reactions in ruthenium(II) trisdiimine complexes: Implications for photoredox catalysis POLYHEDRON Luis, E. T., Iranmanesh, H., Beves, J. E. 2019; 160: 1-9

  View details for DOI 10.1016/j.poly.2018.11.057

  View details for Web of Science ID 000459518800001

• Predictable Substituent Control of Co<SUP>III/II</SUP> Redox Potential and Spin Crossover in Bis(dipyridylpyrrolide)cobalt Complexes INORGANIC CHEMISTRY McPherson, J. N., Hogue, R. W., Akogun, F., Bondi, L., Luis, E. T., Price, J. R., Garden, A. L., Brooker, S., Colbran, S. B. 2019; 58 (3): 2218-2228

  Abstract

  A family of five easily prepared tridentate monoanionic 2,5-dipyridyl-3-(R1)-4-(R2)-pyrrolide anions (dppR1,R2)-, varying in the nature of the R1 and R2 substituents [R1, R2 = CN, Ph; CO2Et, CO2Et; CO2Me, 4-Py; CO2Me, Me; Me, Me], has been used to generate the analogous family of neutral [CoII(dppR1,R2)2] complexes, two of which are structurally characterized at both 100 and 298 K. Both the oxidation and spin states of these complexes can be switched in response to appropriate external stimuli. All complexes, except [CoII(dppMe,Me)2], exhibit gradual spin crossover (SCO) in the solid state, and SCO activity is observed for three complexes in CDCl3 solution. The cobalt(II) centers in the low spin (LS) complexes are Jahn-Teller tetragonally compressed along the pyrrolide-Co-pyrrolide axis. The complexes in their high spin (HS) states are more distorted than in the LS states, as is also usually the case for SCO active iron(II) complexes. The reversible CoIII/II redox potentials are predictably tuned by choice of substituents R1 and R2, from -0.95 (Me,Me) to -0.45 (CN,Ph) V vs Fc+/Fc, with a linear correlation observed between E1/2(CoIII/II) and the Swain-Lupton parameters of the pyrrolide substituents.

  View details for DOI 10.1021/acs.inorgchem.8b03457

  View details for Web of Science ID 000458085900056

  View details for PubMedID 30672281

• Quantifying alkyl chain disorder in crystalline models of lipid bilayers using Raman spectroscopy JOURNAL OF RAMAN SPECTROSCOPY Rich, A. M., Bhattacharyya, S., Aldilla, V. R., Beves, J. E., Bhadbhade, M., Kumar, N., Luis, E. T., Marjo, C. E. 2019; 50 (1): 63-73

  View details for DOI 10.1002/jrs.5501

  View details for Web of Science ID 000456163100007

• Structure-function relationships of donor-acceptor Stenhouse adduct photochromic switches CHEMICAL SCIENCE Mallo, N., Foley, E. D., Iranmanesh, H., Kennedy, A. D. W., Luis, E. T., Ho, J., Harper, J. B., Beves, J. E. 2018; 9 (43): 8242-8252

  Abstract

  The first in-depth, systematic study of the photoswitching properties of Donor-Acceptor Stenhouse Adducts (DASAs) is reported. Barbituric acid derived DASAs functionalised with 14 different amines ranging from dimethylamine to 4-methoxy-N-methylaniline were structurally characterised in solution using 1H and 13C NMR spectroscopy and, in eight cases, in the solid state by single crystal X-ray diffraction. The distribution of coloured and colourless isomers in the dark, their photostationary states under irradiation, apparent thermal half-lives, and fatigue resistance are systematically compared. A simple kinetic model is used to characterise photoswitching behaviour and reveals that minor structural modifications can significantly improve the photoswitching properties of DASA photochromes. These modifications result in excellent photoswitching properties for '1st generation' DASAs in chloroform, including exceptional fatigue resistance, opening the door for these photochromic molecules to find widespread applications.

  View details for DOI 10.1039/c8sc03218a

  View details for Web of Science ID 000449701000010

  View details for PubMedID 30542573

  View details for PubMedCentralID PMC6240811

• Luminescent Tetrahedral Molecular Cages Containing Ruthenium(II) Chromophores INORGANIC CHEMISTRY Luis, E. T., Iranmanesh, H., Arachchige, K. S. A., Donald, W. A., Quach, G., Moore, E. G., Beves, J. E. 2018; 57 (14): 8476-8486

  Abstract

  We have designed linear metalloligands which contain a central photoactive [Ru(N∧N)3]2+ unit bordered by peripheral metal binding sites. The combination of these metalloligands with Zn(II) and Fe(II) ions leads to heterometallic tetrahedral cages, which were studied by NMR spectroscopy, mass spectrometry, and photophysical methods. Like the parent metalloligands, the cages remain emissive in solution. This approach allows direct incorporation of the favorable properties of ruthenium(II) polypyridyl complexes into larger self-assembled structures.

  View details for DOI 10.1021/acs.inorgchem.8b01157

  View details for Web of Science ID 000439250500054

  View details for PubMedID 29969245

• Chiral Ruthenium(II) Complexes as Supramolecular Building Blocks for Heterometallic Self-Assembly INORGANIC CHEMISTRY Iranmanesh, H., Arachchige, K. S. A., Bhadbhade, M., Donald, W. A., Liew, J. Y., Liu, K., Luis, E. T., Moore, E. G., Price, J. R., Yan, H., Yang, J., Beves, J. E. 2016; 55 (24): 12737-12751

  Abstract

  A series of enantiopure ruthenium(II) polypyridyl complexes are reported that feature pendant pyridyl groups suitable for building larger self-assembled structures. The complexes are characterized in detail in solution using NMR spectroscopy, cyclic voltammetry, and photophysical methods and in the solid state using single-crystal X-ray crystallography. The complexes are luminescent, displaying long excited-state lifetimes that are quenched when the pendant pyridyl groups are protonated. Reaction with cadmium(II) ions results in the formation of a mixed-metal one-dimensional coordination polymer, which was characterized by single-crystal X-ray crystallography.

  View details for DOI 10.1021/acs.inorgchem.6b02007

  View details for Web of Science ID 000390294600033

  View details for PubMedID 27989210

• Efficient microwave-assisted synthesis and characterization of key ruthenium(II) polypyridyl complexes [Ru(bpy)₃](PF₆)₂, [Ru(phen)₃](PF₆)₂, [Ru(bpy)₂(phen)](PF₆)₂ and [Ru(phen)₂(bpy)](PF₆)₂ JOURNAL OF COORDINATION CHEMISTRY Luis, E. T., Ball, G. E., Gilbert, A., Iranmanesh, H., Newdick, C. W., Beves, J. E. 2016; 69 (11-13): 1686-1694

  View details for DOI 10.1080/00958972.2016.1194404

  View details for Web of Science ID 000380129800002

• Badly behaving bipyridine: the surprising coordination behaviour of 5,5′-substituted-2,2′-bipyridine towards iron(II) and ruthenium(II) ions SUPRAMOLECULAR CHEMISTRY Iranmanesh, H., Bhadbhade, M., De Haas, N., Luis, E. T., Yan, H., Yang, J., Beves, J. E. 2015; 27 (11-12): 854-864

  View details for DOI 10.1080/10610278.2015.1091938

  View details for Web of Science ID 000365622200015

• Facile, room-temperature pre-treatment of rice husks with tetrabutylphosphonium hydroxide: Enhanced enzymatic and acid hydrolysis yields BIORESOURCE TECHNOLOGY Lau, B. Y., Luis, E. T., Hossain, M. M., Hart, W. S., Cencia-Lay, B., Black, J. J., To, T. Q., Aldous, L. 2015; 197: 252-259

  Abstract

  Aqueous solutions of tetrabutylphosphonium hydroxide have been evaluated as pretreatment media for rice husks, prior to sulphuric acid hydrolysis or cellulase enzymatic hydrolysis. Varying the water:tetrabutylphosphonium hydroxide ratio varied the rate of delignification, as well as silica, lignin and cellulose solubility. Pre-treatment with 60wt% hydroxide dissolved the rice husk and the regenerated material was thus heavily disrupted. Sulphuric acid hydrolysis of 60wt%-treated samples yielded the highest amount of glucose per gram of rice husk. Solutions with good lignin and silica solubility but only moderate to negligible cellulose solubility (10-40wt% hydroxide) were equally effective as pre-treatment media for both acid and enzymatic hydrolysis. However, pre-treatment with 60wt% hydroxide solutions was incompatible with downstream enzymatic hydrolysis. This was due to significant incorporation of phosphonium species in the regenerated biomass, which significantly inhibited the activity of the cellulase enzymes.

  View details for DOI 10.1016/j.biortech.2015.08.056

  View details for Web of Science ID 000361828000034

  View details for PubMedID 26342336