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Quantum-dot/molecule composites (QD/mol) have demonstrated useful photochemical properties for many photonic and optoelectronic applications; however, a comprehensive understanding of these materials remains elusive. This work introduces a series of cadmium(II) selenide/1-pyrenecarboxylic acid (CdSe/PCA) nanomaterials featuring bespoke PCA surface coverage on CdSe585 (coded by the peak of the first exciton absorption band) to glean insight into the QD/mol photophysical behavior. Tailoring the energy gap between the CdSe585 first exciton band (2.1 eV) and the lowest PCA triplet level (T1 = 2.0 eV) to be nearly isoenergetic, strong thermally activated delayed photoluminescence (TADPL) is observed resulting from reverse triplet-triplet energy transfer. The resultant average decay time constant (τobs) of the photoluminescence emanating from CdSe585 is deterministically controlled with surface-bound PCAn chromophores (n = average number of adsorbed PCA molecules) by shifting the triplet excited state equilibrium from the CdSe585 to the PCA molecular triplet reservoir as a function of n.

The steady-state and ultrafast to supra-nanosecond excited state dynamics of fac-[Re(NBI-phen)(CO)3(L)](PF6) (NBI-phen = 16H-benzo[4′,5′]isoquinolino[2′,1′:1,2]imidazo[4,5-f][1,10]phenanthrolin-16-one) as well as their respective models of the general molecular formula [Re(phen)(CO)3(L)](PF6) (L = PPh3 and CH3CN) has been investigated using transient absorption and time-gated photoluminescence spectroscopy. The NBI-phen containing molecules exhibited enhanced visible light absorption with respect to their models and a rapid formation (

A quaternary segmented flow regime for robust and flexible continuous biphasic chemical processes is introduced and characterized for stability and dynamic properties through over 1500 automatically conducted experiments. The flow format is then used for the continuous flow ligand exchange of cadmium selenide quantum dots under high intensity ultraviolet illumination for improved photoluminescence quantum yield.

Thermally activated photophysical processes are ubiquitous in numerous organic and metal-organic molecules, leading to chromophores with excited-state properties that can be considered an equilibrium mixture of the available low-lying states. Relative populations of the equilibrated states are governed by temperature. Such molecules have been devised as high quantum yield emitters in modern organic light-emitting diode technology and for deterministic excited-state lifetime control to enhance chemical reactivity in solar energy conversion and photocatalytic schemes. The recent discovery of thermally activated photophysics at CdSe nanocrystal-molecule interfaces enables a new paradigm wherein molecule-quantum dot constructs are used to systematically generate material with predetermined photophysical response and excited-state properties. Semiconductor nanomaterials feature size-tunable energy level engineering, which considerably expands the purview of thermally activated photophysics beyond what is possible using only molecules. This Perspective is intended to provide a nonexhaustive overview of the advances that led to the integration of semiconductor quantum dots in thermally activated delayed photoluminescence (TADPL) schemes and to identify important challenges moving into the future. The initial establishment of excited-state lifetime extension utilizing triplet-triplet excited-state equilibria is detailed. Next, advances involving the rational design of molecules composed of both metal-containing and organic-based chromophores that produce the desired TADPL are described. Finally, the recent introduction of semiconductor nanomaterials into hybrid TADPL constructs is discussed, paving the way toward the realization of fine-tuned deterministic control of excited-state decay. It is envisioned that libraries of synthetically facile composites will be broadly deployed as photosensitizers and light emitters for numerous synthetic and optoelectronic applications in the near future.

The impact on the morphology nanoceramic materials generated from group 4 metal alkoxides ([M(OR)4]) and the same precursors modified by 6,6'-(((2-hydroxyethyl)azanediyl)bis(methylene))bis(2,4-di- tert-butylphenol) (referred to as H3-AM-DBP2 (1)) was explored. The products isolated from the 1:1 stoichiometric reaction of a series of [M(OR)4] where M = Ti, Zr, or Hf; OR = OCH(CH3)2(OPr i); OC(CH3)3(OBu t); OCH2C(CH3)3(ONep) with H3-AM-DBP2 proved, by single crystal X-ray diffraction, to be [(ONep)Ti( k4( O,O',O'',N)-AM-DBP2)] (2), [(OR)M(μ( O)- k3( O',O'',N)-AM-DBP2)]2 [M = Zr: OR = OPr i, 3·tol; OBu t, 4·tol; ONep, 5·tol; M = Hf: OR = OBu t, 6·tol; ONep, 7·tol]. The product from each system led to a tetradentate AM-DBP2 ligand and retention of a parent alkoxide ligand. For the monomeric Ti derivative (2), the metal was solved in a trigonal bipyramidal geometry, whereas for the Zr (3-5) and Hf (6, 7) derivatives a symmetric dinuclear complex was formed where the ethoxide moiety of the AM-DBP2 ligand bridges to the other metal center, generating an octahedral geometry. High quality density functional theory level gas-phase electronic structure calculations on compounds 2-7 using Gaussian 09 were used for meaningful time dependent density functional theory calculations in the interpretation of the UV-vis absorbance spectral data on 2-7. Nanoparticles generated from the solvothermal treatment of the ONep/AM-DBP2 modified compounds (2, 5, 7) in comparison to their parent [M(ONep)4] were larger and had improved regularity and dispersion of the final ceramic nanomaterials.

The synthesis of a series of lanthanide trifluoroacetic acid (H-TFA) derivatives which contain only the TFA and its conjugate acid has been developed. From the reaction of Ln(N(SiMe3)2)3 with an excess amount of H-TFA, the products were identified as: [Ln(μ-TFA)3(H-TFA)2]n (Ln = Y, Ce, Sm, Eu, Gd, Tb, Dy), [Ln(μ-TFA)3(μ-H-TFA)]n·solv (Ln·solv = Pr·2 H-TFA, H3O+, Ho·2py, Er·py, Yb·py, H-TFA), 3[H][(TFA)La(μ-TFA)3La(TFA)(μ-TFA)2(μc-TFA)2]n ½(H2O) ½(H2O, H-TFA) (La·½(H2O) ½(H2O, H-TFA)), [(k2-TFA)Nd(μ-TFA)3]n·H-py+ (Nd·H-py+), [(py)2Tm(μ-TFA)3]n (Tm), or [Lu(μ-TFA)4Lu(μ-TFA)3·H3O+]n (Lu·H3O+). The majority of samples formed long chain polymers with 3 or 4 μ-TFA ligands. Tm was isolated with py coordinated to the metal, whereas Ho, Er, and Yb were isolated with py located within the lattice. Select samples from this set of compounds were used to generate nanomaterials under solvothermal (SOLVO) conditions using pyridine (py) or octylamine at 185 °C for 24 h. The SOLVO products were isolated as: (i) from py: La – fluocerite (LaF3, PDF 98-000-0214, R = 9.64%, 35(0) nm), Tb – terbium fluoride (TbF3, PDF 00-037-1487, R = 4.76%, 21(2) nm), Lu lutetium oxy fluoride (LuOF, PDF 00-052-0779, R = 8.24%, 8(2) nm); (ii) from octylamine: La – fluocerite/lanthanum oxide carbonate (LaF3, PDF 98-000-0214, R = 7.47%, 5(0) nm; La2O2(CO3), PDF 01-070-5539, R = 12.32%, 12(0) nm), Tb – terbium oxy fluoride (TbOF, PDF 00-008-0230, R = 7.01%, 5(0) nm); Lu – lutetium oxide (Lu2O3, PDF 00-012-0728, R = 6.52%, 6(1) nm).

The synthesis and characterization of a series of group 4 carboxylate derivatives ([M(ORc)4] where M = Ti, Zr, Hf) was undertaken for potential utility as precursors to ceramic nanowires. The attempted syntheses of the [M(ORc)4] precursors were undertaken from the reaction of [M(OBu(t))4] with a select set of carboxylic acids (H-ORc where ORc = OPc (O2CCH(CH3)2), OBc (O2CC(CH3)3), ONc (O2CCH2C(CH3)3)). The products were identified by single-crystal X-ray diffraction studies as [Ti(η(2)-OBc)3(OBu(t))] (1), [Zr2(μ3-O)(μ-OPc)4(μ,η(2)-OPc)(η(2)-OPc)]2 (2), [H]2[Zr(η(2)-OBc)2(OBc)2(OBc)2] (3), [Zr(μ-ONc)2(η(2)-ONc)2]2 (4), or [Hf(μ-ORc)2(η(2)-ORc)2]2 [ORc = OPc (5), OBc (6, shown), ONc (7)]. The majority of compounds (4-7) were isolated as dinuclear species with a dodecahedral-like (CN-8) bonding mode around the metals due to chelation and bridging of the ORc ligand. The two monomers (1 and 3) were found to adopt a capped trigonal prismatic and CN-8 geometry, respectively, due to chelating ORc and terminal ORc or OBu(t) ligands. The metals of the oxo-species 2 were isolated in octahedral and CN-8 arrangements. These compounds were then processed by electrospinning methods (applied voltage 10 kV, flow rate 30-60 μL/min, electric field 0.5 kV/cm), and wire-like morphologies were isolated using compounds 4, 6 (shown), and 7.

Continued exploration of the coordination behavior of derivatives of 2-benzophenone-based ligands with metal alkoxides ([M(OR)4]) was undertaken from the reaction of 2-(2-hydroxy-4-methoxybenzoyl)benzoic acid (H2-OBzA) with a series of Group 4 precursors. The products of these reactions were identified as: [(OR)2Ti(μ-(c,c-OBzA))]2 (OR = OCHMe2 (OPri; 1 •2tol); OCMe3 (OBut; 2 •THF); OCH2CMe3 (ONep; 3)), [[(OPri)3Ti(μ-OPri)Ti(OPri)2]2(μ-(μc,μ-OBzA))2]2 (4), [(ONep)3Zr(μ-ONep)2Zr(ONep)2]2(μ-(c,μ-OBzA)2) (5 •tol), [(py)(OBut)3Zr]2(μ-(c,c-OBzA)) (6), [(OBut)2Hf(μ-OBut)]2(μ-(c,η1-OBzA)) (7) where ‘c’ = chelating or η2; ‘μ’ = bridging or η1,η1(O,O’); and μc = bridging chelating or η1,η1(O,O’); η2 : η1. The metal centers for each of these compounds adopt a pseudo-octahedral geometry employing the OBzA ligand in numerous binding modes. The different functional oxygens (carboxylate, hydroxyl, and carbonyl) were employed in a variety of coordination modes for 1–7. The complexity of these OBzA-modified compounds is d...

A family of crystallographically characterized solvated sodium alkoxides ([(solv)xNa(OR)]n) was synthesized from the reaction of sodium bis(trimethylsilyl)amide with a series of sterically varied aryl alcohols (H–OAr): 2-alkyl phenol [alkyl = methyl (oMP), iso-propyl (oPP), and tert-butyl (oBP)] or 2,6-di-alkyl phenol [alkyl = methyl (DMP), iso-propyl (DIP), and tert-butyl (DBP)]. Single crystal X-ray experiments revealed the structure of the products to be highly dependent on the ligand set employed and the solvent used (THF or py). The [(solv)xNa(OAr)]n products were identified as: [(THF)Na(μ3-oMP)]6 (1), [(THF)4Na6(μ3-oPP)4(μ4-oPP)2] (2), [(THF)Na(μ3-oBP)]4 (3)·THF, [(THF)Na(μ3-DMP)]4 (4), [(THF)2Na(μ-DIP)]2 (5), [(THF)2Na(μ-DBP)]2 (6), {[Na(μ-DPhP-ηx)]2}n (7), [(py)5Na6(μ3-oMP)4(μ4-oMP)2]2[(py)4Na6(μ3-oMP)4(μ4-oMP)2] (8), [(py)6Na4(μ3-oPP)4] (9)·py, [(py)Na(μ3-DMP)]4 (11), [(py)2Na(μ-DIP)]2 (12), [(py)4Na(DBP)] (13). Crystals could not be isolated for the Na/oBP/py (10) system but the powder was assigned the ‘[(py)Na(oBP)]4’ structure based on the available analytical data. In addition, under similar conditions, the neo-pentoxide (ONep) derivatives were isolated and characterized as [(solv)4Na6(μ3-ONep)4(μ4-ONep)2] (solv = THF, 14; py 15). A number of complex structures (monomers, squares, cubes, fused-cubes, hexagons) were observed for this family of [(solv)xNa(OAr)]n compounds. The solution behaviors of these compounds were studied using heteronuclear 23Na NMR. A comparison of these [(solv)xA(OR)]n A = Li, Na, K, Rb, Cs structural motifs is also presented.

A series of rubidium aryloxides, [Rb(OAr)(solv) n ] x , was synthesized from the reaction of Rbo with a select set of 2-alkyl phenols [alkyl = methyl (H-oMP), iso-propyl (H-oPP), and tert-butyl (H-oBP)] and 2,6-di-alkyl phenols [alkyl = methyl (H-DMP), iso-propyl (H-DIP), and tert-butyl (H-DBP)]. The products were identified by single-crystal X-ray diffraction as [Rb5(μx-O)(ηx,μx-oMP)3] n (1), [Rb4(ηx,μx-oPP)4(py)] n (2), [Rb(μ3-oBP)(ηx-tol)]6 (3), [H]2[Rb7(O)(ηx,μ-DMP)7(py)2] n (4), and [Rb(η6,μ x -DIP)] n (5) (where ηx and μx indicate an undetermined amount of the specified interaction). Acceptable crystals of the DBP derivative could not be grown in our hands. In contrast to the solvated polymeric K and unsolvated Cs derivatives, the Rb derivatives were a mixture of solvated and unsolvated polymers and for the first time some were isolated with oxo ligands. NMR studies indicated that these compounds become smaller symmetric species upon dissolution.

The coordination behavior of a set of (ethylenedioxy)diethanamine-based tetraphenol ligands with a series of Group 4 metal alkoxides ([M(OR)(4)]) was determined. The ligands were synthesized from a modified Mannich reaction and fully characterized as N,N,N',N'-tetrakis(3,5-tert-butyl-benzyl-2-hydroxy)-2,2'-(ethylenedioxy)diethanamine, termed H(4)-OEA-DBP(4) (1), and N,N,N',N'-tetrakis(3,5-chloro-benzyl-2-hydroxy)-2,2'-(ethylenedioxy)diethanamine, termed H(4)-OEA-DCP(4) (2). The reaction of 1 with a set of [M(OR)(4)] [M = Ti, Zr, or Hf; OR = iso-propoxide (OPr(i)), neo-pentoxide (ONep), or tert-butoxide (OBu(t))] precursors led to the isolation of [(OPr(i))(2)Ti](2)(μ-OEA-DBP(4)) (3), [(ONep)(2)Ti](2)(μ-OEA-DBP(4)) (4), and [(OBu(t))(2)M](2)(μ-OEA-DBP(4)) where M = Ti (5), Zr (6), or Hf (7). In addition, the [(ONep)(2)Ti](2)(μ-OEA-DCP(4)) (4a) derivative was isolated from the reaction of 2 and [Ti(ONep)(4)], demonstrating the similarity of coordination behavior between the two OEA-R(4) ligands. For 3-7, the metal center adopts a slightly distorted octahedral geometry by binding the two O atoms of the phenoxide moiety, as well as one N and one O atom from the OEA moieties, while retaining two of the original OR ligands. Solution NMR demonstrates inequivalent protons for the majority of the bound OEA ligands, which argues for retention of structure in solution. The synthesis and characterization of these compounds are presented in detail.

Investigation of the coordination behavior of 4,4′-methylenebis(2,6-di-tert-butylphenol) (or H2-4DBP) with a series of metal alkoxides led to isolation of [(OR)3M]2(µ-4DBP), where M/OR = Ti/OBut (2), Ti/ONep (3), Zr/OBut (4), Hf/OBut (5), and [(py)(OR)3M]2(µ-4DBP) · py (5a), where py = pyridine and ONep = OCH2C(CH3)3. Metal alkyl derivatives of 4DBP were also studied and found to form similar di-substituted species: [(py)2(Et)Zn]2(µ-4DBP) · py (6), [(THF)3(Br)Mg]2(µ-4DBP) (7), [(THF)2(Br)Mg](µ-4DBP)[Mg(Br)(THF)3] · (THF, tol) (7a), and [(py)(R)2Al]2(µ-4DBP), where R = CH3 (8), Et (9), CH2CH(CH3)2 (10); tol = toluene and THF = tetrahydrofuran. All structures demonstrate the bridging nature of 4DBP and the ability to bind a variety of metal centers. Solution state NMR indicates that the structures of 2–10 are retained in solution. Thermal analyses indicate that 4DBP is preferentially lost during heating.