Alkoxy Oxygen Research Articles

A highly crystalline face-on π-conjugated polymer based on alkoxythiophene-flanked benzobisthiazole for organic photovoltaics

The use of noncovalent intramolecular interactions constitutes a powerful design strategy for preparing π-conjugated polymers featuring high backbone coplanarities and thereby high crystallinities. Herein, we report the design and synthesis of an alkoxythiophene-flanked benzobisthiazole (BBTz) as a new building unit for π-conjugated polymers, which was subsequently copolymerized to give a simple BBTz-bithiophene copolymer with alkyl and alkoxy groups (PDBTz2). Owing to the S···O noncovalent intramolecular interactions between the alkoxy oxygens and thiazole sulfurs in BBTz, PDBTz2 showed greater coplanarity and crystallinity than its alkyl counterpart, PDBTz1. Interestingly, the backbone orientation was completely altered from the edge-on orientation observed for PDBTz1 to a face-on orientation for PDBTz2, which is preferable for organic photovoltaics (OPVs). In addition, the electron-donating nature of the alkoxy group increased the HOMO energy level of PDBTz2 compared to that of PDBTz1, which enabled photoinduced hole transfer from a nonfullerene acceptor, Y6, to the polymer. As a result, the short-circuit current density of an organic photovoltaic cell based on PDBTz2 and Y6 was significantly greater than that of a cell based on PDBTz1 and Y6. This study confirmed that alkoxythiophene-flanked BBTz is a promising building unit for high-performance π-conjugated polymers.

Rational Design of F-Modified Polyester Electrolytes for Sustainable All-Solid-State Lithium Metal Batteries.

Solid polymer electrolytes (SPEs) are one of the most practical candidates for solid-state batteries owing to their high flexibility and low production cost, but their application is limited by low Li+ conductivity and a narrow electrochemical window. To improve performance, it is necessary to reveal the structure-property relationship of SPEs. Here, 23 fluorinated linear polyesters were prepared by editing the coordination units, flexible linkage segments, and interface passivating groups. Besides the traditionally demonstrated coordinating capability and flexibility of polymer chains, the molecular asymmetry and resulting interchain aggregation are observed critical for Li+ conductivity. By tailoring the molecular asymmetry and coordination ability of polyesters, the Li+ conductivity can be raised by 10 times. Among these polyesters, solvent-free poly(pentanediol adipate) delivers the highest room-temperature Li+ conductivity of 0.59 × 10-4 S cm-1. The chelating coordination of oxalate and Li+ leads to an electron delocalization of alkoxy oxygen, enhancing the antioxidation capability of SPEs. To lower the cost, high-value LiTFSI in SPEs is recycled at 90%, and polyesters can be regenerated at 86%. This work elucidates the structure-property relationship of polyester-based SPEs, displays the design principles of SPEs, and provides a way for the development of sustainable solid-state batteries.

Mechanistic Details of the Titanium-Mediated Polycondensation Reaction of Polyesters: A DFT Study

In this work, the mechanism of polyester polycondensation catalysed by titanium catalysts was investigated using density functional theory (DFT). Three polyester polycondensation reaction mechanisms, including the Lewis acid mechanism (M1), the coordination of the ester alkoxy oxygen mechanism (M2) and the coordination of the carboxy oxygen mechanism (M3), were investigated. Three reaction mechanisms for the polycondensation reaction of diethyl terephthalate (DET) were investigated using Ti(OEt)4 and cationic Ti(OEt)3+ as the catalyst. The results show that the polycondensation reaction of the Lewis acid mechanism exhibits similar energy barriers to the catalyst-free condition (42.6 kcal/mol vs. 47.6 kcal/mol). Mechanism M3 gives the lowest energy barrier of 17.5 kcal/mol, indicating that Ti(OEt)4 is the active centre for the polycondensation reaction. The catalytic efficiency of Ti(OEt)3+ is lower than that of Ti(OEt)4 catalysts due to its higher DET distortion energy (67.6 kcal/mol vs. 37.4 kcal/mol) by distortion–interaction analysis.

Tungsten minerals flotation with 4-alkoxy benzohydroxamic acid: The structure-performance relationship of its C3 derivatives

To improve the flotation recovery of tungsten minerals, 4-alkoxy benzohydroxamic acids containing C3 alkyl (C3OBs), namely 4-propoxy benzohydroxamic acid (POB), 4-iso-propoxy benzohydroxamic acid (IPOB) and 4-allyloxy hydroxamic acid (AOB), were designed as scheelite and wolframite collectors. The micro-flotation results uncovered that C3OBs exhibited stronger collecting ability towards Pb(Ⅱ)-activated scheelite and wolframite than benzohydroxamic acid (BHA) and the collecting ability of C3OBs was in sequence of POB > IPOB > AOB. The density functional theory (DFT) calculation indicated that the alkoxy oxygen atom of C3OBs contributed to their highest occupied molecular orbital (HOMO), and the HOMO energy followed the order as IPOB > POB > AOB > BHA. The higher HOMO energy, the stronger electron-donating activity. Nevertheless, IPOB didn’t return the highest flotation recovery of tungsten minerals. On the other hand, the hydrophobicity of these four hydroxamate collectors was in sequence of POB > IPOB > AOB > BHA, corresponding to the results of contact angle, micro-flotation and adsorption capacity. Therefore, the hydrophobization of the four hydroxamate collectors played a key role in their flotation performance to the Pb(II)-activated scheelite and wolframite. Moreover, this work offered a new approach for developing superior collectors.

Heterogenous Preparations of Solution-Processable Cobalt Phthalocyanines for Carbon Dioxide Reduction Electrocatalysis

The development and implementation of technology that can capture and transform carbon dioxide (CO2) is of ongoing interest. To that end, the integration of molecular electrocatalysts into devices is appealing because of the desirable features of molecules, such as the ability to modify active sites. Here, we explore how the identity of the aliphatic group in 1,4,8,11,15,18,22,25-octaalkoxyphthalocyanine cobalt(II) affects the catalytic behavior for heterogeneous CO2 reduction electrocatalysis. The alkyl R-groups correspond to n-butoxy, sec-butoxy, and 2-ethylhexoxy. All of the catalysts are soluble in organic solvents and are readily solution-processed. However, the larger 2-ethylhexoxy group showed solution aggregation behavior at concentrations ≥1 mM, and it was, in general, an inferior catalyst. The other two catalysts show comparable maximum currents, but the octa sec-butoxy-bearing catalyst showed larger CO2 reduction rate constants based on foot-of-the-wave analyses. This behavior is hypothesized to be due to the ability of the sec-butoxy groups to eliminate the ability of the alkoxy oxygen to block Co Sites via ligation. CO2 reduction activity is rationalized based on solid-state structures. Cobalt(II) phthalocyanine and its derivatives are known to be good CO2 reduction catalysts, but the results from this work suggest that straightforward incorporation of bulky groups can improve the processability and per site activity by discouraging aggregation.

Vibrational study of hydrated methyl formate complexes in solid neon: Observation for the first time of three isomers for methyl formate-water complex

Methyl formate (MF) is an important interstellar medium molecule and it has been the subject of several theoretical and experimental studies in literature. The experimental study of the complexation of this molecule with water has never been undertaken from a vibrational point of view as well as the homodimer (MF)2. We highlight for the first time the presence of three isomers for the (MF)2, MF-H2O and MF-(H2O)2 complexes in solid neon. For the MF-H2O complex, we observe without ambiguity three isomers: two where the carbonyl oxygen served as the proton acceptor and one where the alkoxy oxygen was the proton acceptor. For the MF-(H2O)2 complex, we clearly observe three isomers especially by the observation of large frequency shifts of two MF modes. Theoretical calculations at the second-order Møller-Plesset level have been performed to obtain the equilibrium geometries and vibrational spectra at the harmonic level and comparison with experimental data allows us to give structures of observed complexes.

Novel Heteroleptic Tin(II) Complexes Capable of Forming SnO and SnO2 Thin Films Depending on Conditions Using Chemical Solution Deposition.

A new heteroleptic complex series of tin was synthesized by the salt metathesis reaction of SnX2 (X = Cl, Br, and I) with aminoalkoxide and various N-alkoxy-functionalized carboxamide ligands. The complexes, [ClSn(dmamp)]2 (1), [BrSn(dmamp)]2 (2), and [ISn(dmamp)]2 (3), were prepared from the salt metathesis reaction of SnX2 with one equivalent of dmamp; [Sn(dmamp)(empa)]2 (4), [Sn(dmamp)(mdpa)]2 (5), and [Sn(dmamp)(edpa)]2 (6) were prepared via the salt metathesis reaction using complex 2 with one equivalent of N-alkoxy-functionalized carboxamide ligand. Complexes 1–5 displayed dimeric molecular structures with tin metal centers interconnected by μ2–O bonding via the alkoxy oxygen atom. The molecular structures of complexes 1–5 showed distorted trigonal bipyramidal geometries with lone pair electrons in the equatorial position. Using complex 6 as a tin precursor, SnOx films were deposited by chemical solution deposition (CSD) and subsequent post-deposition annealing (PDA) at high temperatures. SnO and SnO2 films were selectively obtained under controlled PDA atmospheres of argon and oxygen, respectively. The SnO films featured a tetragonal romarchite structure with high crystallinity and a preferred growth orientation along the (101) plane. They also exhibited a lower transmittance of >52% at 400 nm due to an optical band gap of 2.9 eV. In contrast, the SnO2 films exhibited a tetragonal cassiterite crystal structure and an extremely high transmittance of >97% at 400 nm was observed with an optical band gap of 3.6 eV.

Synthesis of Heteroleptic Zinc Complexes Containing Aminoalkoxide and β‐Diketonate Ligands

AbstractNew heteroleptic complexes of zinc were designed and synthesized using aminoalkoxide and β‐diketonate ligands. The complexes, [Zn(dmamp)(tmhd)]2 (1), [Zn(dmamp)(acac)]2 (2), [Zn(dmamp)(hfac)]2 (3), [Zn(dmamb)(tmhd)]2 (4), [Zn(dmamb)(acac)]2 (5), and [Zn(dmamb)(hfac)]2 (6), were synthesized by controlled acid‐base reactions between [EtZn(aminoalkoxide)]2 and β‐diketonate ligands. Single crystal x‐ray diffraction showed that complexes 1−4 and 6 exist as dimeric molecular structures with the zinc metal centers interconnected by the alkoxy oxygen atom via μ2‐O bonding and their gemetries exhibit distorted trigonal bipyrimidal. TGA curves of complexes 3 and 6 showed sharp weight losses in a single step with very low residues, which confirmed the excellent vaporization and thermal stability.

Formation of Tetranuclear Nickel(II) Complexes with Schiff-Bases: Crystal Structures and Magnetic Properties

The cubane-type structure is a typical representative of tetranuclear coordination compounds. In this work, two anionic Schiff-base ligands, (L1)2− and (L2)2−, each offering an O^N^O coordination pocket, ligate four NiII ions into a [Ni4O4] cubane core. The ligands are H2L1 = 2−[[(3-ethoxy-2−hydroxyphenyl) methylene]amino]benzenemethanol and H2L2 = 2−[[(5-fluoro-2−hydroxyphenyl)methylene]amino]benzenemethanol. In both compounds, [Ni4(L1)4(EtOH)4] (1) and [Ni4(L2)4(MeOH)4] (2), alkoxy oxygens of the ligands act in a bridging μ3-O binding mode. Magnetic susceptibility and magnetization data for compounds 1 and 2 are presented. The Ni–O–Ni bond angles of the cubane core determined from single crystal X-ray diffraction data play a key role for a magneto-structural correlation. Dominant intracube ferromagnetic behavior is observed, and the coupling parameters were determined for both compounds, leading to nonzero spin ground states in accordance with the broadly accepted bond angle guideline.

N–H⋯O hydrogen bonding to the alkoxy oxygen of a carboxylic ester group: crystal structures of methyl 2,6-diaminobenzoate and its derivatives

Molecules with hydrogen bonds from amino groups to both oxygens of a carboxylic ester are described, and other examples of hydrogen bonding to an ester's alkoxy oxygen atom are highlighted.

Synthesis, Crystal Structure, Mesophase Behaviour and Optical Property of Azo-ester Bridged Compounds

Azo-ester mesogen containing two liquid crystalline compounds C1-C2 having polymerizable acrylate functional group as the terminal were designed and synthesized. The chemical structures and purity of the synthesized compounds were confirmed by different spectroscopic techniques such as FT-IR, 1H NMR and 13C NMR. X-ray crystal structure showed that compound C1 exhibited more stable E configuration with two bulky groups in the opposite sides of the N=N double bond motifs. The 1, 2-diphenyldiazene fragment in the structure of C1 is essentially planar with RMS deviation from planarity of 0.0555 Å. Analysis of the crystal packing of compound C1 revealed its intriguing supramolecular sheet-like multilayer molecular packing stabilized by C-H…O interaction involving the phenyl and acryloyl hydrogen with the carbonyl oxygen and alkoxy oxygen atoms. Thermogravimetric investigation demonstrated that both of the compounds exhibited excellent thermal stability and their thermal degradation was influenced by the terminal substituent. The DSC and POM studies confirmed that compounds C1-C2 exhibited enantiotropic liquid crystalline mesophase behaviour. Optical investigations demonstrated that both of the compounds showed strong absorption band around 300-420 nm and exhibited blue fluorescence emission.

How To Achieve High Regioselectivity in Barrier-less Nucleophilic Addition to p-Benzynes Generated via Bergman Cyclization of Unsymmetrical Cyclic Azaenediyne?

Inducing high regioselectivity in nucleophilic addition to p-benzynes, first reported by Perrin and O'Connor et al. ( J. Am. Chem. Soc. 2007 , 129 , 4795 - 4799 ) has been a challenge as the reaction involves a very fast barrier-less addition of nucleophile. On the other hand, achieving a high degree of regioselectivity is important as that will make the reaction synthetically useful. Recently, a study has been reported from our group ( J. Org. Chem. 2018 , 83 , 7730 - 7740 ), whereby it was shown that nucleophilic addition to p-benzynes derived from unsymmetrical N-substituted cyclic enediynes proceeds with low extent of selectivity by incorporation of groups with divergent electronic characters. Herein, we report that excellent regioselectivity (>99%) can be achieved keeping an ortho alkoxy group in unsymmetrical 1,2-dialkynylbenzene in the form of a cyclic enediyne in quantitative yields. High regioselectivity (∼84%) is also shown by pyridine based enediynes where the pyridine nitrogen is in a 1,3-relationship with the impending radical center, expanding the synthetic scope of this nucleophilic addition. The regioselectivity can be explained in terms of computed electrostatic potentials which are substantially different around two radical centers arising due to the "ortho effect" (conformational alignment of lone pair of the ortho alkoxy oxygen or the nitrogen in pyridine systems).

New Heteroleptic Cobalt Precursors for Deposition of Cobalt-Based Thin Films.

A new series of heteroleptic complexes of cobalt were synthesized using aminoalkoxide and β-diketonate ligands. The complexes, [Co(dmamp)(acac)]2 (3), [Co(dmamp)(tfac)]2 (4), [Co(dmamp)(hfac)]2 (5), [Co(dmamp)(tmhd)]2 (6), and [Co(dmamb)(tmhd)]2 (7), were prepared by two-step substitution reactions and studied using Fourier transform infrared spectroscopy, mass spectrometry, elemental analysis, and thermogravimetric analysis (TGA). Complexes 3–7 displayed dimeric molecular structures for all of the complexes with cobalt metal centers interconnected by μ2-O bonding by the alkoxy oxygen atom. TGA and a thermal study of the complexes displayed high volatilities and stabilities for complexes 6 and 7, with sublimation temperatures of 120 °C/0.5 Torr and 130 °C/0.5 Torr, respectively.

Tetracopper complexes with two-mode cubane-like Cu4O4 core from similar hydroxyl-rich salicylaldehyde Schiff bases: Structure and magnetic properties

The reaction of water-soluble hydroxyl-rich salicylaldehyde Schiff base ligands with the metal salt Cu(OAc)2·H2O affords three novel tetracopper complexes via solvothermal method: [Cu4(H2L1)4]·CH3OH(1), [Cu4(HL2)2(Py)2(OAc)2](2), [Cu4(HL3)2(Py)2(OAc)2](3). The X-ray crystal structures reveal the cubane Cu4O4 for complex 1 with μ3-alkoxo bridges and quasi-stepped cubane Cu4O4 for 2 and 3 bearing two central copper atoms bridged by two alkoxy groups and two peripheral copper atoms bridged with central copper atoms by one another alkoxy oxygen. Temperature-dependent magnetic measurements indicate that the dominant ferromagnetic interactions among metal ions within the cubic core of 1 with J1=+27.44cm−1, J2=−0.21cm−1 (g=2.1157) while there are antiferromagnetic interactions between two metal centers in 3 with J1=−268cm−1, J2=−297cm−1 (g=2.068).

Structure–activity relations of leucine derivatives reveal critical moieties for cellular uptake and activation of mTORC1-mediated signaling

Among amino acids, leucine is a potential signaling molecule to regulate cell growth and metabolism by activating mechanistic target of rapamycin complex 1 (mTORC1). To reveal the critical structures of leucine molecule to activate mTORC1, we examined the structure-activity relationships of leucine derivatives in HeLa S3 cells for cellular uptake and for the induction of phosphorylation of p70 ribosomal S6 kinase 1 (p70S6K), a downstream effector of mTORC1. The activation of mTORC1 by leucine and its derivatives was the consequence of two successive events: the cellular uptake by L-type amino acid transporter 1 (LAT1) responsible for leucine uptake in HeLa S3 cells and the activation of mTORC1 following the transport. The structural requirement for the recognition by LAT1 was to have carbonyl oxygen, alkoxy oxygen of carboxyl group, amino group and hydrophobic side chain. In contrast, the requirement for mTORC1 activation was more rigorous. It additionally required fixed distance between carbonyl oxygen and alkoxy oxygen of carboxyl group, and amino group positioned at α-carbon. L-Configuration in chirality and appropriate length of side chain with a terminal isopropyl group were also important. This confirmed that LAT1 itself is not a leucine sensor. Some specialized leucine sensing mechanism with rigorous requirement for agonistic structures should exist inside the cells because leucine derivatives not transported by LAT1 did not activate mTORC1. Because LAT1-mTOR axis is involved in the regulation of cell growth and cancer progression, the results from this study may provide a new insight into therapeutics targeting both LAT1 and leucine sensor.

Modeling Vibrational Spectra of Ester Carbonyl Stretch in Water and DMSO Based on Molecular Dynamics Simulation.

On the basis of molecular dynamics simulation, we model the ester carbonyl stretch FTIR signals of methyl acetate in D2O and DMSO. An ab initio map is constructed at the B3LYP/6-311++G** level to relate the carbonyl stretch frequency to the external electric field. Using this map, fluctuating Hamiltonian of the carbonyl stretch is constructed from the MD simulation trajectory. The IR spectra calculated based on this Hamiltonian are found to be in good agreement with the experiment. For methyl acetate in D2O, hydrogen bonding on alkoxy oxygen causes a blue shift of frequency, while that on carbonyl oxygen causes a red shift. Two peaks observed in FTIR signals originate from the balance of these two effects. Furthermore, in both D2O and DMSO solutions, correlations are found between the instantaneous electric field on C═O and the frequencies. Broader line width of the signal in D2O suggests a more inhomogeneous electric field distribution due to the complicated hydrogen-bonding environment.

Self-Assembly of Cations in Aqueous Solutions of Hydroxyl-Functionalized Ionic Liquids: Molecular Dynamics Studies.

The effect of presence of a hydroxyl-functionalized alkyl chain of varying carbon number on the self-assembly of cations in aqueous solutions of 1-(n-hydroxyalkyl)-3-decylimidazolium bromide (where the alkyl groups are ethyl, butyl, heptyl, and decyl) has been studied using atomistic molecular dynamics simulations. Spontaneous self-assembly of cations to form aggregates with hydrophobic core and hydrophilic surface is observed. The shape of the aggregates changes from quasispherical in the case of cations with hydroxyheptyl or smaller substituent chain, to a thin film like intercalated aggregate in the case of cations with hydroxydecyl chain. Cations with hydroxydecyl substituent chain exhibit long-range spatial correlations, and the anions are associated with cations to a greater extent due to the higher surface charge density of the aggregate. The ordered film like aggregate is stabilized by the dispersion interactions between the intercalated substituent chains and the intermolecular hydrogen bonds formed between the alkoxy oxygen atoms and the hydrogen atoms of the imidazolium ring. The cations form less compact aggregates with lower aggregation number than their nonhydroxyl analogues in the corresponding aqueous solutions. The intracationic and aggregate structures are governed by the length of the hydroxyalkyl chain.

Crystal structure of patatin-17 in complex with aged and non-aged organophosphorus compounds.

Patatin is a non-specific plant lipase and the eponymous member of a broad class of serine hydrolases termed the patatin-like phospholipase domain containing proteins (PNPLAs). Certain PNPLA family members can be inhibited by organophosphorus (OP) compounds. Currently, no structural data are available on the modes of interaction between the PNPLAs and OP compounds or their native substrates. To this end, we present the crystal structure of patatin-17 (pat17) in its native state as well as following inhibition with methyl arachidonyl fluorophosphonate (MAFP) and inhibition/aging with diisopropylphosphorofluoridate (DFP). The native pat17 structure revealed the existence of two portals (portal1 and portal2) that lead to its active-site chamber. The DFP-inhibited enzyme underwent the aging process with the negatively charged phosphoryl oxygen, resulting from the loss of an isopropyl group, being within hydrogen-binding distance to the oxyanion hole. The MAFP-inhibited pat17 structure showed that MAFP did not age following its interaction with the nucleophilic serine residue (Ser77) of pat17 since its O-methyl group was intact. The MAFP moiety is oriented with its phosphoryl oxygen in close proximity to the oxyanion hole of pat17 and its O-methyl group located farther away from the oxyanion hole of pat17 relative to the DFP-bound state. The orientation of the alkoxy oxygens within the two OP compounds suggests a role for the oxyanion hole in stabilizing the emerging negative charge on the oxygen during the aging reaction. The arachidonic acid side chain of MAFP could be contained within portals 1 or 2. Comparisons of pat17 in the native, inhibited, and aged states showed no significant global conformational changes with respect to their Cα backbones, consistent with observations from other α/β hydrolases such as group VIIA phospholipase A2.

Heterometallic Pentanuclear [Ni4Ln] (LnIII = Gd, Tb, Dy, Ho) Complexes: Accidental Orthogonality Leading to Ferromagnetic Interactions

AbstractThe reaction of 6‐formyl‐2‐(hydroxymethyl)‐4‐methylphenol (LH2) with NiII and LnIII salts afforded a series of heterometallic pentanuclear compounds [Ni4Ln(L)4(OAc)2(MeOH)4](NO3)(MeOH) [LnIII = Gd (1), Dy (2), Tb (3), Ho (4)]. Four dianionic L2– ligands and two acetate anions hold together four NiII and one LnIII ion to form a Ni4Ln core possessing a distorted tetrahedral geometry. All the NiII ions are hexacoordinate (6 O) with a distorted octahedral geometry whereas the LnIII ion is octacoordinate (8 O) with a distorted square‐antiprism geometry. All the NiII ions are connected to the central LnIII ion through μ2 bridging of one deprotonated phenolic oxygen and two deprotonated alkoxy oxygen atoms. The magnetic properties of 1–4 were investigated in the temperature range 2–300 K. The magnetic properties of 1 were fitted by using a Hamiltonian containing isotropic exchange, NiII local zero‐field‐splitting, and Zeeman effects (Ĥ = Ĥexchange + Ĥzfs + Ĥzeeman). The molecular structures of 1–4 reveal that the Ni–O–Ln angle is around 89° whereas the Ni–O–Ni angle is about 96°. Because of this accidental orthogonality, ferromagnetic interactions between the nearest‐neighbor NiII ions and between NiII and LnIII ions have been observed. The observed J values are 0.34 and 1.88 cm–1 between GdIII–NiII and NiII–NiII, respectively.

A density functional theory model of mechanically activated silyl ester hydrolysis.

To elucidate the mechanism of the mechanically activated dissociation of chemical bonds between carboxymethylated amylose (CMA) and silane functionalized silicon dioxide, we have investigated the dissociation kinetics of the bonds connecting CMA to silicon oxide surfaces with density functional calculations including the effects of force, solvent polarizability, and pH. We have determined the activation energies, the pre-exponential factors, and the reaction rate constants of candidate reactions. The weakest bond was found to be the silyl ester bond between the silicon and the alkoxy oxygen atom. Under acidic conditions, spontaneous proton addition occurs close to the silyl ester such that neutral reactions become insignificant. Upon proton addition at the most favored position, the activation energy for bond hydrolysis becomes 31 kJ mol(-1), which agrees very well with experimental observation. Heterolytic bond scission in the protonated molecule has a much higher activation energy. The experimentally observed bi-exponential rupture kinetics can be explained by different side groups attached to the silicon atom of the silyl ester. The fact that different side groups lead to different dissociation kinetics provides an opportunity to deliberately modify and tune the kinetic parameters of mechanically activated bond dissociation of silyl esters.